[!!!][TASK] Remove unused tabmenu JavaScript and CSS

Due to the shift to the new tabmenu logic, all leftover code
that is unused is now removed.

Releases: master
Resolves: #69795
Change-Id: Ia875c2938dc852b478e49be82bf2922ce67ab165
Reviewed-on: http://review.typo3.org/43301


Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>