[TASK] Fix phpdoc of FileRepository

Resolves: #76881
Releases: master, 7.6, 6.2
Change-Id: I168cc72209c9a61c3101cb2aeeb52d7344231029
Reviewed-on: https://review.typo3.org/48738


Tested-by: Bamboo TYPO3com <info@typo3.com>
Reviewed-by: Oliver Klee <typo3-coding@oliverklee.de>
Reviewed-by: Andreas Fernandez <typo3@scripting-base.de>
Tested-by: Andreas Fernandez <typo3@scripting-base.de>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>