fix(Popup): proptypes for content and trigger

[miroslavstastny]

Fixes #1419.

Expected behavior (provided by PR's changes)

It is possible to use content + children.
It is not possible to use trigger + children.

[bmdalex]

👍 I was about to create issue on this one, thanks for fixing!

[codecov]

Codecov Report

Merging #1420 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #1420      +/-   ##
==========================================
+ Coverage   73.59%   73.59%   +<.01%     
==========================================
  Files         787      787              
  Lines        5888     5889       +1     
  Branches     1717     1737      +20     
==========================================
+ Hits         4333     4334       +1     
  Misses       1549     1549              
  Partials        6        6

Impacted Files	Coverage Δ
packages/react/src/components/Popup/Popup.tsx	67.74% <ø> (ø)	⬆️
packages/react-proptypes/src/index.ts	33.81% <100%> (+0.47%)	⬆️

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