[TASK] Replace prophecy in EXT:core RootlineUtilityTest

Resolves: #98766
Releases: main
Change-Id: I26a0f9f904493eb8d5a682bb0254a4b8fe28f668
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/76750


Reviewed-by: Stefan Bürk <stefan@buerk.tech>
Reviewed-by: Oliver Klee <typo3-coding@oliverklee.de>
Tested-by: core-ci <typo3@b13.com>
Tested-by: Oliver Klee <typo3-coding@oliverklee.de>
Tested-by: Stefan Bürk <stefan@buerk.tech>