fix: Fixed popup CSS styling

[andrewnester]

Issue #, if available:

Description of changes:
Fixed popup CSS styling

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[codecov]

Codecov Report

Merging #4728 (5c3c54b) into master (f269889) will decrease coverage by 0.05%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #4728      +/-   ##
==========================================
- Coverage   71.15%   71.10%   -0.06%     
==========================================
  Files         554      554              
  Lines       55693    55693              
  Branches    10421    10421              
==========================================
- Hits        39630    39602      -28     
- Misses      16063    16091      +28     

Flag	Coverage Δ
unittests	71.10% <ø> (-0.06%)	⬇️

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Impacted Files	Coverage Δ
lib/ace/autocomplete/popup.js	78.19% <ø> (ø)
lib/ace/editor.js	79.66% <0.00%> (-1.98%)	⬇️
lib/ace/mode/php_completions.js	26.08% <0.00%> (ø)

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