[TASK] Commit compiled install.css

Make compiling css with grunt clean again when executing.

Resolves: #79794
Releases: master
Change-Id: Iafee078446347e1de834f555439c921fc401aa98
Reviewed-on: https://review.typo3.org/51663


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>