[TASK] TYPO3 Coding Guidelines - Including files with "include_once" is not allowed; use "require_once" instead

Change-Id: Ia3a79381b24ca9b615bccc9b96ea94377e5e29cc
Resolves: #54684
Reviewed-on: https://review.typo3.org/26608
Reviewed-by: Alex Kellner
Tested-by: Alex Kellner