[flexiglass] Disables KeyguardStateCallbackInteractorTest when flexi on

The class under test has documentation to suggest that it will be
removed once Flexiglass is enabled so no need to test it with flexi on.

Bug: 283121968
Test: not really
Flag: EXEMPT test only
Change-Id: I4e5c5a1fd5b1472f7cd5b1bd97f40e6483b635f0