Change @dataprovider to static in FileCacheFactoryTest

Here we don't use the mock at all so we can just provide a concrete class as an alternative test implementation.

Seems like a good refactor.

Looks good. Committed/pushed to 11.x and cherry-picked to 10.3.x, thanks!

catch → closed merge request !7733

Automatically closed - issue fixed for 2 weeks with no activity.