[TASK] Use static constant call for PageRepository

Minor fix to use the static constant directly, like in all other usages.

Resolves: #85559
Releases: master
Change-Id: I163bea97ddd78b6f37945daaf7aecaab6c47bdff
Reviewed-on: https://review.typo3.org/57599


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Joerg Boesche <typo3@joergboesche.de>
Tested-by: Joerg Boesche <typo3@joergboesche.de>
Reviewed-by: Markus Klein <markus.klein@typo3.org>
Tested-by: Markus Klein <markus.klein@typo3.org>