Tweak ChatMessage margins

[ahuang11]

Without the divider, the reaction icons were too far left.

Then I noticed that the chat copy icon and reaction icons were misaligned vertically.

I also noticed that the chat copy icon and reaction icons inline spacing were somewhat different (more space between each reaction icon vs reaction icons + chat copy icon)

So I tweaked it all:

Before:

After:

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 82.19%. Comparing base (d4f7d68) to head (aede3ca).
Report is 22 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #7310   +/-   ##
=======================================
  Coverage   82.18%   82.19%           
=======================================
  Files         337      337           
  Lines       50380    50394   +14     
=======================================
+ Hits        41407    41422   +15     
+ Misses       8973     8972    -1     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[philippjfr]

I really don't think making single pixel adjustments is the correct way to fix this, but for now it's an improvement and I'll merge.