[TASK] Avoid invalid method ValidatorResolverTest

"dummy" is not a valid method in the mocked class.

Resolves: #100482
Related: #100249
Releases: main
Change-Id: Ic0c13044350beae6cbc7bca67406e8d1c50cfe84
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/78489


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