fix(teams-theme): replace margins with padding in chatItemStyles (Teams theme)

[mnajdova]

Replace margins with padding in chatItemStyles for Teams theme, for correct calculation of the height when using it together with virtualized lists.

[codecov]

Codecov Report

Merging #878 into master will not change coverage.
The diff coverage is 0%.

@@           Coverage Diff           @@
##           master     #878   +/-   ##
=======================================
  Coverage   80.59%   80.59%           
=======================================
  Files         648      648           
  Lines        8334     8334           
  Branches     1484     1484           
=======================================
  Hits         6717     6717           
  Misses       1602     1602           
  Partials       15       15

Impacted Files	Coverage Δ
...src/themes/teams/components/Chat/chatItemStyles.ts	38.46% <0%> (ø)	⬆️

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