[TASK] Replace prophecy in EXT:form FormManagerControllerTest

Resolves: #98977
Releases: main
Change-Id: Ib83b762e61483783695e04cdb2257f40ddf14b0a
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/76914


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