[TASK] Replace prophecy in EXT:form TranslationServiceTest

Resolves: #98906
Releases: main
Change-Id: I4c2a52e5ab69001bae4a1a8aa67d9612be4a73e2
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/76841


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