[BUGFIX] Typos in t3skin css files

Remove the lines as they have not been valid, nobody will miss them.

Resolves: #57716
Releases: 6.3, 6.2
Change-Id: I70625980ec49f6a8f76d695c4e2eb5d3c1548b36
Reviewed-on: https://review.typo3.org/30329
Reviewed-by: Markus Klein
Tested-by: Markus Klein