[CLEANUP] Update comment of PageRepository::getMountPointInfo()

Update the comment of the mehtod PageRepository::getMountPointInfo().
Add hint addressing to the usage of recursive mount points.

Change-Id: I095563cb940e25f8c5f004497d407733faf4cbcc
Releases: master, 8.7
Resolves: #81254
Reviewed-on: https://review.typo3.org/52845


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>