[TASK] Simplify usages of LanguageService->sL

A few places still manually check for "LLL:" as
prefix. This is now resolved, as all of this is
already done in LanguageService directly.

Resolves: #96926
Releases: main
Change-Id: Icee5060a5d5b48177e9a5440fcab5d50e3dc9036
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/73561


Tested-by: core-ci <typo3@b13.com>
Tested-by: Stefan Bürk <stefan@buerk.tech>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Stefan Bürk <stefan@buerk.tech>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>