fix(button group): revert margin update

[bmdalex]

fix(button group): revert margin update

Description

This PR fixes a small regression in the spacing of Button.Group component items, introduced #945

Screenshots

Before:

After:

[codecov]

Codecov Report

Merging #973 into master will decrease coverage by 0.17%.
The diff coverage is 66.66%.

@@            Coverage Diff             @@
##           master     #973      +/-   ##
==========================================
- Coverage   80.96%   80.78%   -0.18%     
==========================================
  Files         665      665              
  Lines        8504     8504              
  Branches     1433     1433              
==========================================
- Hits         6885     6870      -15     
- Misses       1604     1620      +16     
+ Partials       15       14       -1

Impacted Files	Coverage Δ
...ckages/react/src/components/Button/ButtonGroup.tsx	97.22% <ø> (-0.08%)	⬇️
...hemes/teams/components/Button/buttonGroupStyles.ts	36.36% <66.66%> (+6.36%)	⬆️
packages/react/src/components/Flex/Flex.tsx	50% <0%> (-44.12%)	⬇️

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