[BUGFIX] Use correct hook name for mime type guessers

Resolves: #85641
Related: #60019
Releases: master, 8.7, 7.6
Change-Id: If9c94c020da6991dc070fa6aa8395042686b2752
Reviewed-on: https://review.typo3.org/57679


Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>
Reviewed-by: Markus Klein <markus.klein@typo3.org>
Tested-by: Markus Klein <markus.klein@typo3.org>
Tested-by: TYPO3com <no-reply@typo3.com>