[TASK] Strictify Tests part 3 - backend

Resolves: #94867
Releases: master
Change-Id: Ibb0f7aefcdcf7b2fffd5b181287befaf8ee20074
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/70543


Tested-by: core-ci <typo3@b13.com>
Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>