fix(chatBehavior): Use FocusZone mode Embed instead of Wrap

[sophieH29]

FocusZone renders redundant

in Wrap mode for chat. This PR changes mode to Embed to simplify HTML structure

[codecov]

Codecov Report

Merging #1044 into master will decrease coverage by 0.05%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1044      +/-   ##
==========================================
- Coverage   81.77%   81.71%   -0.06%     
==========================================
  Files         687      687              
  Lines        8822     8822              
  Branches     1566     1566              
==========================================
- Hits         7214     7209       -5     
- Misses       1593     1598       +5     
  Partials       15       15

Impacted Files	Coverage Δ
...c/lib/accessibility/Behaviors/Chat/chatBehavior.ts	92.85% <ø> (+7.14%)	⬆️
packages/react/src/lib/renderComponent.tsx	92.59% <0%> (-4.94%)	⬇️
...ct/test/specs/commonTests/handlesAccessibility.tsx	83.09% <0%> (-1.41%)	⬇️
...ages/react/test/specs/commonTests/isConformant.tsx	93.08% <0%> (-0.47%)	⬇️

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[layershifter]

Changelog entry?

[mnajdova]

Please update the changelog entry :)