Don't make an IPC to set the initialValue of isFingerprintEnabledByDevicePolicy

Instead, we can make the StateFlow a Flow to avoid requiring a
initialValue. The value was only used in the dumpsys for debugging.

Test: atest BiometricSettingsRepositoryTest
Fixes: 327277125
Flag: None
Change-Id: Ieda62c8d694d35a60fc2073cd5bde09c210eb331