fix(debugger): change debug test icon

[rcoringrato-sfdc]

What does this PR do?

Correct the icon for the debug test action of the test side bar when using light themes

What issues does this PR fix or reference?

@W-8880441@

[codecov]

Codecov Report

Merging #2978 (cbd0d81) into develop (190b45d) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff            @@
##           develop    #2978   +/-   ##
========================================
  Coverage    75.91%   75.91%           
========================================
  Files          275      275           
  Lines        10495    10495           
  Branches      1221     1221           
========================================
  Hits          7967     7967           
  Misses        2192     2192           
  Partials       336      336           

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