[TASK] Followup: Use t3skin-icons for DomainObject-editor

Previous commit mixed up save- and close-icons.

Change-Id: I0509f4eebf180269ec87a21d3443b87cedae49a9
Resolves: #57432
Reviewed-on: https://review.typo3.org/29183
Reviewed-by: Stefan Neufeind
Tested-by: Stefan Neufeind