[BUGFIX] Fix type in BackendUserAuthentication->check

Resolves: #100183
Releases: main
Change-Id: I4aa8d6f35046cbd77ad67a6c44a6f6f38f7b4ea5
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/78778


Tested-by: Georg Ringer <georg.ringer@gmail.com>
Reviewed-by: Oliver Klee <typo3-coding@oliverklee.de>
Tested-by: Oliver Klee <typo3-coding@oliverklee.de>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: core-ci <typo3@b13.com>