[BUGFIX] PHP 8 warnings from installer

Some rather obvious sanitation around
TYPO3 installation procedure.

Resolves: #94443
Releases: master
Change-Id: Icb358cafbf6216d436358b7b45273f907deba721
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/69670


Tested-by: core-ci <typo3@b13.com>
Tested-by: Oliver Bartsch <bo@cedev.de>
Tested-by: Jochen <rothjochen@gmail.com>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Oliver Bartsch <bo@cedev.de>
Reviewed-by: Jochen <rothjochen@gmail.com>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>