[BUGFIX] Exclude current record when checking slug's uniqueness

The current record constraint was forgotten in the
implementation of uniqueInTable and is now added.

Resolves: #91378
Related: #91235
Releases: master, 9.5
Change-Id: Ie7862b22a06996a9d7ca484a01d7a1859c8f7276
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/64482


Tested-by: Helmut Hummel <typo3@helhum.io>
Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Benni Mack <benni@typo3.org>
Reviewed-by: Helmut Hummel <typo3@helhum.io>
Reviewed-by: Susanne Moog <look@susi.dev>
Reviewed-by: Benni Mack <benni@typo3.org>