[CLEANUP] Cleanup phpDoc in ext:frontend

Resolves: #62771
Releases: master
Change-Id: I6f79bd66765dc5fef0ac331d79855cb9ea3d8a39
Reviewed-on: http://review.typo3.org/33889
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>