[TASK] Cleanup WorkspaceSelectorToolbarItem

Resolves: #59748
Releases: 6.3
Change-Id: I29ff785404fba56ccff0a5e909c8dd1149c4a9bb
Reviewed-on: https://review.typo3.org/30970
Reviewed-by: Robert van Kammen
Tested-by: Robert van Kammen
Reviewed-by: Christian Kuhn
Tested-by: Christian Kuhn