D23069: Remove disabled TabGroup feature

GB_2 added a comment.


  In D23069#527002 <https://phabricator.kde.org/D23069#527002>, @gladhorn wrote:
  
  > I can do the UI changes (and I don't mind re-basing the change if the other one goes in first). Should I squash the UI changes into this patch or create a new change?
  
  
  I think it's best if the improved UI lands first and then you remove the complete feature with the UI after that in this patch.

REPOSITORY
  R108 KWin

REVISION DETAIL
  https://phabricator.kde.org/D23069

To: gladhorn, #kwin
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