[TASK] Remove unused $arrayConstraint in IndexerServiceTest

The array was used by a mock call which is removed from
the test.

Resolves: #56119
Releases: 6.2
Change-Id: I6aa5ad720a52a710e59b9570a769396d6acb37fb
Reviewed-on: https://review.typo3.org/27821
Reviewed-by: Wouter Wolters
Tested-by: Wouter Wolters
Reviewed-by: Stefano Kowalke
Tested-by: Stefano Kowalke