[TASK] Remove tests no longer needed

Category API was changed to silently fail instead of throwing an
exception, but the corresponding tests were not removed.

Releases: 6.2
Resolves: #58416
Relates: #58384
Change-Id: I52c0fac32c7f4385868ef5f28c6f94b583948e75
Reviewed-on: https://review.typo3.org/29772
Reviewed-by: Frans Saris
Tested-by: Frans Saris
Reviewed-by: Christian Kuhn
Tested-by: Christian Kuhn