Replace deprecated AndroidJUnit4.

AndroidJUnit4 from `androidx.test.runner` is deprecated, use
`androidx.test.ext.junit.runners.AndroidJUnit4` instead. See https://
developer.android.com/reference/androidx/test/runner/AndroidJUnit4 for
more details.

Bug: 354063239
Test: atest FrameworksCoreTests:DecorContextTest FrameworksCoreTests:PhoneWindowTest
Flag: TEST_ONLY
Change-Id: I3aa3f9ad7edeb328cd7d007ea74c66ad1f80d06e
2 files changed