[TASK] Replace prophecy in EXT:core FailsafeContainerTest

Resolves: #98763
Releases: main
Change-Id: I1e254429777594b5035c24d46f7ca5cb5ea3a219
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/76697


Tested-by: core-ci <typo3@b13.com>
Tested-by: Oliver Klee <typo3-coding@oliverklee.de>
Tested-by: Torben Hansen <derhansen@gmail.com>
Reviewed-by: Torben Hansen <derhansen@gmail.com>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>