Minor bug fixes for Lockscreen Safety Center source

- use correct severity enum for issues
- update biomterics on lockscreen change
- clean up some nearby tests to use eq matcher instead of captor

Test: SettingsUnitTests
Test: Manually tested
Bug: 223170514
Bug: 222338885
Change-Id: I4e28a418473cbe7cd5d75daf0d62776654fa7917