Re-enable biometric prompt tests.

These were temporarily disabled when the face-to-fingerprint flow was replaced with the coex flow. The test refactor caused presubmit failures because the detach method was not called after the test ended, which could cause unrelated downstream tests to fail.

Bug: 222119218
Test: atest AuthBiometricViewTest
Change-Id: Ie6c18ab2fabe6f42cff9706ad51062ebbad82bd0