[Pod] Don't reference SystemUIAppComponentFactory in keyguard directly

Eventually KeyguardSliceProvider and SystemUIAppComponentFactoryBase
will be in different build targets, so don't import the latter into the
former.

Bug: 307607958
Flag: EXEMPT refactor
Test: compiles
Change-Id: I2736fb6a85cda6b19adfdd819c2738b19d001a31