fixes #4179 removed control highlight from disconnect button

[mcarare]

set colorControlHighlight to transparent in activity theme.
property cannot be set in view because it is overwritten by activity theme.

Pull Request checklist

• Quality: This PR builds and passes detekt/ktlint checks (A pre-push hook is recommended)
• [] Tests: This PR includes thorough tests or an explanation of why it does not
• Changelog: This PR includes a changelog entry or does not need one
• Accessibility: The code in this PR follows accessibility best practices or does not include any user facing features

[codecov-io]

Codecov Report

Merging #4806 into master will increase coverage by 0.01%.
The diff coverage is n/a.

@@             Coverage Diff             @@
##             master   #4806      +/-   ##
===========================================
+ Coverage      6.37%   6.39%   +0.01%     
  Complexity      154     154              
===========================================
  Files           205     205              
  Lines          9022    9014       -8     
  Branches       1358    1358              
===========================================
+ Hits            575     576       +1     
+ Misses         8401    8392       -9     
  Partials         46      46

Impacted Files	Coverage Δ	Complexity Δ
...ug/java/org/mozilla/fenix/DebugFenixApplication.kt	0% <0%> (ø)	0% <0%> (ø)	⬇️
app/src/main/java/org/mozilla/fenix/ext/Context.kt	20% <0%> (+4%)	0% <0%> (ø)	⬇️

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