[Fixes #5073] Update install docs

[t-book]

• Correct Tomcat Version
• Fix gzip compression for js

Fixes #5073
Closes #5073

• Confirm you have read the contribution guidelines
• You have sent a Contribution Licence Agreement (CLA) as necessary (not required for small changes, e.g., fixing typos in documentation)
• Make sure the first PR targets the master branch, eventual backports will be managed later. This can be ignored if the PR is fixing an issue that only happens in a specific branch, but not in newer ones.

The following are required only for core and extension modules (they are welcomed, but not required, for contrib modules):

• There is a ticket in https://github.com/GeoNode/geonode/issues describing the issue/improvement/feature (a notable exemptions is, changes not visible to end users)
• The issue connected to the PR must have Labels and Milestone assigned
• PR for bug fixes and small new features are presented as a single commit
• Commit message must be in the form "[Fixes #<issue_number>] Title of the Issue"
• New unit tests have been added covering the changes, unless there are explanation on why the tests are not necessary/implemented
• This PR passes all existing unit tests (test results will be reported by travis-ci after opening this PR)
• This PR passes the QA checks: flake8 geonode
• Commits changing the settings, UI, existing user workflows, or adding new functionality, need to include documentation updates

Submitting the PR does not require you to check all items, but by the time it gets merged, they should be either satisfied or inapplicable.

[codecov]

Codecov Report

Merging #5074 into master will not change coverage.
The diff coverage is n/a.

@@          Coverage Diff           @@
##           master   #5074   +/-   ##
======================================
  Coverage    59.6%   59.6%           
======================================
  Files         139     139           
  Lines       14129   14129           
  Branches     2147    2147           
======================================
  Hits         8422    8422           
  Misses       4983    4983           
  Partials      724     724

[backporting]

The backport to 2.10.x failed:

Commits ["17cc5c767a4df811539e47395db0bbfd4e6fde03","0bb703c93dc2f4b8ef289b31e75c00b7736d48f1"] could not be cherry-picked on top of 2.10.x

To backport manually, run these commands in your terminal:

# Fetch latest updates from GitHub.
git fetch
# Create new working tree.
git worktree add .worktrees/backport 2.10.x
# Navigate to the new directory.
cd .worktrees/backport
# Cherry-pick all the commits of this pull request and resolve the likely conflicts.
git cherry-pick 17cc5c767a4df811539e47395db0bbfd4e6fde03 0bb703c93dc2f4b8ef289b31e75c00b7736d48f1
# Create a new branch with these backported commits.
git checkout -b backport-5074-to-2.10.x
# Push it to GitHub.
git push --set-upstream origin backport-5074-to-2.10.x
# Go back to the original working tree.
cd ../..
# Delete the working tree.
git worktree remove .worktrees/backport

Then, create a pull request where the base branch is 2.10.x and the compare/head branch is backport-5074-to-2.10.x.