Fix merge issue in ToolStripRenderer (Sizing Grip).

[KlausLoeffelmann]

Fixing a merge issue in the context of the large DarkMode merge.
(Has already been merged into the Preivew6 branch.)

Microsoft Reviewers: Open in CodeFlow

[codecov]

Codecov Report

Attention: Patch coverage is 87.87879% with 4 lines in your changes missing coverage. Please review.

Project coverage is 76.59673%. Comparing base (6249f64) to head (d94ed48).
Report is 1 commits behind head on main.

Additional details and impacted files

@@                 Coverage Diff                 @@
##                main      #13620         +/-   ##
===================================================
- Coverage   76.59768%   76.59673%   -0.00096%     
===================================================
  Files           3253        3253                 
  Lines         640992      640996          +4     
  Branches       47439       47439                 
===================================================
- Hits          490985      490982          -3     
- Misses        146473      146480          +7     
  Partials        3534        3534                 

Flag	Coverage Δ
Debug	76.59673% <87.87879%> (-0.00096%)	⬇️
integration	18.49270% <0.00000%> (-0.00620%)	⬇️
production	51.04328% <87.87879%> (-0.00175%)	⬇️
test	97.41175% <ø> (ø)
unit	48.44863% <87.87879%> (+0.00628%)	⬆️

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