Switch the mocking session strictness to WARN from STRICT KeyguardUpdateMonitorTest

The stubbing is not great in this test, not all flows are stubbed out properly,
if a device is not provisioned when the test runs, mockito complains quite a bit
about either unmatched stubs or unnecessary stubbing.

Bug: 277873197
Test: atest KeyguardUpdateMonitorTest
Test: force mDeviceProvisioned flag to false in KeyguardUpdateMonitor
      run the test, it should not fail
Change-Id: I5adf4e50e1fa93807dc2e6bab53ddc78963605f6