[TASK] Avoid usage of LanguageService->includeLLFile in ext:backend elementBrowser

All usage of globally loaded labels has been replaced,
so the usage of the function to load the labels globally
can safely be removed.

Resolves: #100645
Releases: main
Change-Id: I22f3aec7fd18eb20409dc0d8cd7af8d8bb2f822b
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/78695


Reviewed-by: Christoph Lehmann <christoph.lehmann@networkteam.com>
Reviewed-by: Jörg Bösche <typo3@joergboesche.de>
Tested-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: core-ci <typo3@b13.com>
Tested-by: Christoph Lehmann <christoph.lehmann@networkteam.com>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>