[BUGFIX] Properly update reference index when deleting children

When deleting children in a relation, reference index rows
pointing to a child must be updated, otherwise dangling
reference index rows are left, leading to all kinds of trouble.

Change-Id: I8e8086846ae53c5a32aafc553b6ea66d4a17d7fb
Resolves: #67676
Releases: master, 10.4
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/65809


Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Benni Mack <benni@typo3.org>
Tested-by: Oliver Bartsch <bo@cedev.de>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Benni Mack <benni@typo3.org>
Reviewed-by: Oliver Bartsch <bo@cedev.de>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>