[TASK] Cleanup: Must use "self::" for local static member reference

Resolves: #47925
Releases: 6.2,6.1
Change-Id: I8b23f014fb215a262801480bd4bda3bc44f8c11c
Reviewed-on: https://review.typo3.org/20501
Reviewed-by: Georg Ringer
Tested-by: Georg Ringer