7/n: Fix templating for biometric utils

For some reason, Face/Fingerprint utils were still using
generic BiometricAuthenticator.Identifier instead of its
implemented subclasses (Fingerprint/Face).

Bug: 170497736
Test: No effect on existing devices. Able to rename and remove
      existing templates. Able to add new templates.
Change-Id: I599dbcd3b1244df90880b4272f9e062b12c1ffe4