[TASK] Remove warnings in form documentation rendering

Additionally, remove outdated manuals from list in Settings.cfg.

Resolves: #100641
Releases: main, 11.5
Change-Id: Idc09d4da5a0131ae9d4554790d6f782a87d8da5a
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/78577


Tested-by: core-ci <typo3@b13.com>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>