Fix Issue & Pull Request comment headers on mobile

[kolaente]

This PR fixes the Issue and PR comment headers on mobile. The changes I made also work on desktop which is why I didn't use media queries. This has the nice side effect to make the header look good in edge cases where user's have really long names which wouldn't fit the header even on desktop.

We could also discuss hiding the avatar completely and let the comments take the full width on mobile (like github does) but that would be a separate change.

Before:

After:

[codecov-commenter]

Codecov Report

Merging #13039 into master will decrease coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master   #13039      +/-   ##
==========================================
- Coverage   42.62%   42.60%   -0.02%     
==========================================
  Files         672      672              
  Lines       73785    73785              
==========================================
- Hits        31448    31439       -9     
- Misses      37247    37253       +6     
- Partials     5090     5093       +3     

Impacted Files	Coverage Δ
modules/indexer/stats/db.go	60.86% <0.00%> (-8.70%)	⬇️
modules/log/event.go	56.60% <0.00%> (-0.95%)	⬇️
models/gpg_key.go	53.33% <0.00%> (-0.58%)	⬇️
services/pull/pull.go	40.78% <0.00%> (-0.50%)	⬇️

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