[firebase_auth] Test firebase_auth_platform_interface_test is order-dependent

[enetor]

Internal bug: b/151523518

When running test cases in a particular order, test case "FirebaseAuthPlatform.MethodChannelFirebaseAuth" fails consistently.

[Ehesp]

Hey @enetor - could you send over some additional details? Seems like that's an internal bug report. We can take a look if we know what tests are failing.

Thanks