Fix regression setting gutter tooltip classname

[akoreman]

Issue: #5209

Description of changes: When calling setTheme we overrode the ace_gutter-tooltip class we set to the gutter tooltip.

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[codecov]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (538b18c) 87.19% compared to head (12e5aef) 87.19%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #5211   +/-   ##
=======================================
  Coverage   87.19%   87.19%           
=======================================
  Files         565      565           
  Lines       45121    45122    +1     
  Branches     6910     6910           
=======================================
+ Hits        39342    39343    +1     
  Misses       5779     5779           

Flag	Coverage Δ
unittests	87.19% <100.00%> (+<0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
src/mouse/default_gutter_handler.js	72.97% <100.00%> (+0.18%)	⬆️

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