[CLEANUP] Namespace cleanup in TypoScriptFrontendController

Fix small leftovers after ::class change.

Resolves: #64022
Releases: master
Change-Id: I6873492921cd2205fa621da8842fa186d485e4df
Reviewed-on: http://review.typo3.org/35618
Reviewed-by: Markus Klein <klein.t3@reelworx.at>
Tested-by: Markus Klein <klein.t3@reelworx.at>
Reviewed-by: Oliver Klee <typo3-coding@oliverklee.de>
Reviewed-by: Frank Nägler <typo3@naegler.net>
Tested-by: Frank Nägler <typo3@naegler.net>