[BUGFIX] Follow up foreign_match_fields not fully supported

On detaching related objects the foreign_match_fields needs
to be cleared.

Resolves: #47694
Relates: #45337
Releases: 6.2, 6.1
Change-Id: I6d74201afc437a2b0e2a73022bc71ed0cd1dd2d4
Reviewed-on: https://review.typo3.org/29430
Reviewed-by: Anja Leichsenring
Tested-by: Anja Leichsenring