[stable5.0] FullCalendar CSS: make events in weekly view have the correct width

[backportbot]

Backport of PR #6269

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 15.45%. Comparing base (86b6ef1) to head (ce780fb).
Report is 3 commits behind head on stable5.0.

Additional details and impacted files

@@            Coverage Diff             @@
##           stable5.0    #6270   +/-   ##
==========================================
  Coverage      15.45%   15.45%           
==========================================
  Files            205      205           
  Lines           9426     9426           
  Branches        2189     2188    -1     
==========================================
  Hits            1457     1457           
  Misses          7654     7654           
  Partials         315      315           

Flag	Coverage Δ
javascript	15.45% <ø> (ø)

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