[docs] Revert upgrade to next 9

[eps1lon]

In case renaming the route isn't a positive tradeoff.

Closes #16754

[mui-pr-bot]

@material-ui/core: parsed: +0.54% , gzip: +0.69%
@material-ui/lab: parsed: +0.01% , gzip: +0.52%
@material-ui/styles: parsed: +0.96% , gzip: +0.36%

Details of bundle changes.

Comparing: d4c7c05...6e34fc4

bundle	parsed diff	gzip diff	prev parsed	current parsed	prev gzip	current gzip
@material-ui/core	+0.54% 🔺	+0.69% 🔺	327,279	329,032	90,300	90,920
@material-ui/core/Paper	+0.74% 🔺	+0.30% 🔺	68,218	68,722	20,410	20,472
@material-ui/core/Paper.esm	-0.02%	+0.01% 🔺	61,994	61,984	19,220	19,222
@material-ui/core/Popper	0.00%	-0.11%	28,963	28,963	10,428	10,417
@material-ui/core/Textarea	0.00%	+0.08% 🔺	5,541	5,541	2,371	2,373
@material-ui/core/TrapFocus	0.00%	+0.12% 🔺	3,808	3,808	1,600	1,602
@material-ui/core/styles/createMuiTheme	+0.01% 🔺	+0.02% 🔺	16,161	16,162	5,814	5,815
@material-ui/core/useMediaQuery	0.00%	-0.38%	3,101	3,101	1,317	1,312
@material-ui/lab	+0.01% 🔺	+0.52% 🔺	141,941	141,956	43,683	43,909
@material-ui/styles	+0.96% 🔺	+0.36% 🔺	51,628	52,124	15,408	15,463
@material-ui/system	+0.04% 🔺	-0.18%	15,573	15,579	4,439	4,431
Button	-0.08%	+0.02% 🔺	79,805	79,740	24,362	24,366
Modal	-0.08%	-1.97%	14,643	14,632	5,229	5,126
Portal	0.00%	-0.06%	3,484	3,484	1,565	1,564
Rating	-0.09%	-0.02%	70,558	70,491	22,099	22,094
Slider	-0.01%	-0.03%	75,332	75,323	23,344	23,338
colorManipulator	0.00%	0.00%	3,904	3,904	1,543	1,543
docs.landing	-0.07%	+0.13% 🔺	52,093	52,056	13,814	13,832
docs.main	+0.40% 🔺	+0.26% 🔺	604,388	606,831	193,891	194,397
packages/material-ui/build/umd/material-ui.production.min.js	0.00%	0.00%	301,614	301,614	86,717	86,717
docs: /	-100.00%	-100.00%	56,000	0	-1	0
docs: /_app	-100.00%	-100.00%	137,000	0	-1	0
docs: /_error	-100.00%	-100.00%	2,110	0	-1	0
docs: /blog/2019-developer-survey-results	-100.00%	-100.00%	13,600	0	-1	0
docs: /blog/april-2019-update	-100.00%	-100.00%	4,620	0	-1	0
docs: /blog/june-2019-update	-100.00%	-100.00%	2,200	0	-1	0
docs: /blog/march-2019-update	-100.00%	-100.00%	3,180	0	-1	0
docs: /blog/material-ui-v4-is-out	-100.00%	-100.00%	22,600	0	-1	0
docs: /blog/may-2019-update	-100.00%	-100.00%	2,750	0	-1	0
docs: /components/about-the-lab	-100.00%	-100.00%	6,370	0	-1	0
docs: /components/app-bar	-100.00%	-100.00%	135,000	0	-1	0
docs: /components/autocomplete	-100.00%	-100.00%	291,000	0	-1	0
docs: /components/avatars	-100.00%	-100.00%	27,000	0	-1	0
docs: /components/badges	-100.00%	-100.00%	61,500	0	-1	0
docs: /components/bottom-navigation	-100.00%	-100.00%	26,900	0	-1	0
docs: /components/box	-100.00%	-100.00%	32,800	0	-1	0
docs: /components/breadcrumbs	-100.00%	-100.00%	97,400	0	-1	0
docs: /components/buttons	-100.00%	-100.00%	236,000	0	-1	0
docs: /components/cards	-100.00%	-100.00%	72,900	0	-1	0
docs: /components/checkboxes	-100.00%	-100.00%	69,300	0	-1	0
docs: /components/chips	-100.00%	-100.00%	115,000	0	-1	0
docs: /components/click-away-listener	-100.00%	-100.00%	13,300	0	-1	0
docs: /components/container	-100.00%	-100.00%	13,300	0	-1	0
docs: /components/css-baseline	-100.00%	-100.00%	20,100	0	-1	0
docs: /components/dialogs	-100.00%	-100.00%	224,000	0	-1	0
docs: /components/dividers	-100.00%	-100.00%	51,000	0	-1	0
docs: /components/drawers	-100.00%	-100.00%	229,000	0	-1	0
docs: /components/expansion-panels	-100.00%	-100.00%	83,700	0	-1	0
docs: /components/grid	-100.00%	-100.00%	153,000	0	-1	0
docs: /components/grid-list	-100.00%	-100.00%	57,300	0	-1	0
docs: /components/hidden	-100.00%	-100.00%	55,100	0	-1	0
docs: /components/icons	-100.00%	-100.00%	146,000	0	-1	0
docs: /components/links	-100.00%	-100.00%	50,500	0	-1	0
docs: /components/lists	-100.00%	-100.00%	157,000	0	-1	0
docs: /components/menus	-100.00%	-100.00%	89,400	0	-1	0
docs: /components/modal	-100.00%	-100.00%	37,300	0	-1	0
docs: /components/no-ssr	-100.00%	-100.00%	15,800	0	-1	0
docs: /components/paper	-100.00%	-100.00%	9,510	0	-1	0
docs: /components/pickers	-100.00%	-100.00%	196,000	0	-1	0
docs: /components/popover	-100.00%	-100.00%	70,100	0	-1	0
docs: /components/popper	-100.00%	-100.00%	118,000	0	-1	0
docs: /components/portal	-100.00%	-100.00%	12,100	0	-1	0
docs: /components/progress	-100.00%	-100.00%	103,000	0	-1	0
docs: /components/radio-buttons	-100.00%	-100.00%	58,800	0	-1	0
docs: /components/rating	-100.00%	-100.00%	51,600	0	-1	0
docs: /components/selects	-100.00%	-100.00%	170,000	0	-1	0
docs: /components/slider	-100.00%	-100.00%	80,200	0	-1	0
docs: /components/snackbars	-100.00%	-100.00%	121,000	0	-1	0
docs: /components/speed-dial	-100.00%	-100.00%	55,400	0	-1	0
docs: /components/steppers	-100.00%	-100.00%	208,000	0	-1	0
docs: /components/switches	-100.00%	-100.00%	77,900	0	-1	0
docs: /components/tables	-100.00%	-100.00%	756,000	0	-1	0
docs: /components/tabs	-100.00%	-100.00%	168,000	0	-1	0
docs: /components/text-fields	-100.00%	-100.00%	314,000	0	-1	0
docs: /components/textarea-autosize	-100.00%	-100.00%	9,750	0	-1	0
docs: /components/toggle-button	-100.00%	-100.00%	22,300	0	-1	0
docs: /components/tooltips	-100.00%	-100.00%	96,000	0	-1	0
docs: /components/transfer-list	-100.00%	-100.00%	48,800	0	-1	0
docs: /components/transitions	-100.00%	-100.00%	58,400	0	-1	0
docs: /components/typography	-100.00%	-100.00%	39,700	0	-1	0
docs: /components/use-media-query	-100.00%	-100.00%	60,600	0	-1	0
docs: /customization/breakpoints	-100.00%	-100.00%	80,500	0	-1	0
docs: /customization/color	-100.00%	-100.00%	99,900	0	-1	0
docs: /customization/components	-100.00%	-100.00%	165,000	0	-1	0
docs: /customization/default-theme	-100.00%	-100.00%	55,500	0	-1	0
docs: /customization/density	-100.00%	-100.00%	39,700	0	-1	0
docs: /customization/globals	-100.00%	-100.00%	19,800	0	-1	0
docs: /customization/palette	-100.00%	-100.00%	57,500	0	-1	0
docs: /customization/spacing	-100.00%	-100.00%	12,600	0	-1	0
docs: /customization/themes	-100.00%	-100.00%	62,800	0	-1	0
docs: /customization/typography	-100.00%	-100.00%	428,000	0	-1	0
docs: /customization/z-index	-100.00%	-100.00%	9,730	0	-1	0
docs: /discover-more/backers	-100.00%	-100.00%	6,840	0	-1	0
docs: /discover-more/changelog	-100.00%	-100.00%	3,560	0	-1	0
docs: /discover-more/community	-100.00%	-100.00%	5,440	0	-1	0
docs: /discover-more/governance	-100.00%	-100.00%	6,800	0	-1	0
docs: /discover-more/languages	-100.00%	-100.00%	10,600	0	-1	0
docs: /discover-more/related-projects	-100.00%	-100.00%	18,800	0	-1	0
docs: /discover-more/roadmap	-100.00%	-100.00%	6,590	0	-1	0
docs: /discover-more/showcase	-100.00%	-100.00%	72,600	0	-1	0
docs: /discover-more/team	-100.00%	-100.00%	22,800	0	-1	0
docs: /discover-more/vision	-100.00%	-100.00%	19,100	0	-1	0
docs: /getting-started/example-projects	-100.00%	-100.00%	24,000	0	-1	0
docs: /getting-started/faq	-100.00%	-100.00%	154,000	0	-1	0
docs: /getting-started/installation	-100.00%	-100.00%	31,600	0	-1	0
docs: /getting-started/learn	-100.00%	-100.00%	37,200	0	-1	0
docs: /getting-started/supported-components	-100.00%	-100.00%	73,800	0	-1	0
docs: /getting-started/supported-platforms	-100.00%	-100.00%	23,800	0	-1	0
docs: /getting-started/templates	-100.00%	-100.00%	18,000	0	-1	0
docs: /getting-started/templates/album	-100.00%	-100.00%	10,800	0	-1	0
docs: /getting-started/templates/blog	-100.00%	-100.00%	33,500	0	-1	0
docs: /getting-started/templates/checkout	-100.00%	-100.00%	51,900	0	-1	0
docs: /getting-started/templates/dashboard	-100.00%	-100.00%	391,000	0	-1	0
docs: /getting-started/templates/pricing	-100.00%	-100.00%	22,500	0	-1	0
docs: /getting-started/templates/sign-in	-100.00%	-100.00%	49,400	0	-1	0
docs: /getting-started/templates/sign-in-side	-100.00%	-100.00%	49,700	0	-1	0
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docs: /getting-started/templates/sticky-footer	-100.00%	-100.00%	2,080	0	-1	0
docs: /getting-started/usage	-100.00%	-100.00%	32,200	0	-1	0
docs: /guides/api	-100.00%	-100.00%	62,100	0	-1	0
docs: /guides/composition	-100.00%	-100.00%	104,000	0	-1	0
docs: /guides/flow	-100.00%	-100.00%	6,690	0	-1	0
docs: /guides/interoperability	-100.00%	-100.00%	187,000	0	-1	0
docs: /guides/migration-v0x	-100.00%	-100.00%	52,300	0	-1	0
docs: /guides/migration-v3	-100.00%	-100.00%	131,000	0	-1	0
docs: /guides/minimizing-bundle-size	-100.00%	-100.00%	45,500	0	-1	0
docs: /guides/responsive-ui	-100.00%	-100.00%	14,400	0	-1	0
docs: /guides/right-to-left	-100.00%	-100.00%	49,800	0	-1	0
docs: /guides/server-rendering	-100.00%	-100.00%	58,500	0	-1	0
docs: /guides/testing	-100.00%	-100.00%	53,900	0	-1	0
docs: /guides/typescript	-100.00%	-100.00%	80,100	0	-1	0
docs: /performance/table-component	-100.00%	-100.00%	1,340	0	-1	0
docs: /performance/table-emotion	-100.00%	-100.00%	25,900	0	-1	0
docs: /performance/table-hook	-100.00%	-100.00%	1,420	0	-1	0
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docs: /premium-themes/onepirate/forgot-password	-100.00%	-100.00%	83,400	0	-1	0
docs: /premium-themes/onepirate/privacy	-100.00%	-100.00%	76,200	0	-1	0
docs: /premium-themes/onepirate/sign-in	-100.00%	-100.00%	83,800	0	-1	0
docs: /premium-themes/onepirate/sign-up	-100.00%	-100.00%	84,000	0	-1	0
docs: /premium-themes/onepirate/terms	-100.00%	-100.00%	99,000	0	-1	0
docs: /premium-themes/paperbase	-100.00%	-100.00%	59,600	0	-1	0
docs: /styles/advanced	-100.00%	-100.00%	241,000	0	-1	0
docs: /styles/api	-100.00%	-100.00%	126,000	0	-1	0
docs: /styles/basics	-100.00%	-100.00%	89,700	0	-1	0
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docs: /system/display	-100.00%	-100.00%	59,800	0	-1	0
docs: /system/flexbox	-100.00%	-100.00%	70,100	0	-1	0
docs: /system/palette	-100.00%	-100.00%	29,400	0	-1	0
docs: /system/positions	-100.00%	-100.00%	23,800	0	-1	0
docs: /system/shadows	-100.00%	-100.00%	23,400	0	-1	0
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Generated by 🚫 dangerJS against 6e34fc4

[oliviertassinari]

@eps1lon Thanks for preparing the PR ❤