[TASK] Replace prophecy in EXT:form ClosureFinisherTest

Resolves: #98907
Releases: main
Change-Id: I475b245a83a29e3993dfd47652dfbdb8c0527e0e
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/76327


Reviewed-by: Oliver Klee <typo3-coding@oliverklee.de>
Reviewed-by: Nikita Hovratov <nikita.h@live.de>
Tested-by: core-ci <typo3@b13.com>
Tested-by: Oliver Klee <typo3-coding@oliverklee.de>
Tested-by: Nikita Hovratov <nikita.h@live.de>