[TASK] Avoid loose type comparison in PageLinkBuilder

There are currently 3 conditions in `PageLinkBuilder` which
use loose type comparison. All 3 conditions can safely be
replaced by strict type comparison.

Resolves: #102071
Releases: main
Signed-off-by: Torben Hansen <derhansen@gmail.com>
Change-Id: I4454cd01cecfb402b3819b3dc98e492cb4bfd8b5
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/81302


Tested-by: Simon Schaufelberger <simonschaufi+typo3@gmail.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: Oliver Klee <typo3-coding@oliverklee.de>
Reviewed-by: Oliver Klee <typo3-coding@oliverklee.de>
Reviewed-by: Simon Schaufelberger <simonschaufi+typo3@gmail.com>
Tested-by: core-ci <typo3@b13.com>