Fix response code checks in LockSettingsServiceTests

Some of the test cases compared
VerifyCredentialResponse#getResponseCode() with
GateKeeperResponse#RESPONSE_*.  But that's the wrong "enum"; the values
just happen to be the same.  Use the correct one.

Test: atest FrameworksServicesTests:com.android.server.locksettings
Bug: 395976735
Flag: TEST_ONLY
Change-Id: Ic77dcdb3888a118f3f45a478287a30bef4dcb9aa