[TASK] Update PHPStan

PHPStan 1.8.1 removes one warning.

Used commands:

> composer req --dev phpstan/phpstan:^1.8.1
> ./Build/Scripts/runTests.sh -s phpstanGenerateBaseline

Resolves: #97959
Releases: main, 11.5
Change-Id: Ifaaf37add767f98d16b3e847447a2882c3c77ee8
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/75208


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>