Skip FGS system dialer grant when no dialer role present.

Some tests were failing related to this; ensure we don't run the test
on a device with no dialer role.

Test: This change updates the test.
Flag: android.app.system_dialer_phone_call_fgs_grant
Bug: 435713951
Bug: 425971621
Change-Id: I17100982d77e92655dac11d2ce7a62478d5e9c41