Use FooterPreference in xml explicitly

Removed the FooterPreferenceMixin from the ChooseLockGeneric page.

Fixes: 139269907
Test: manual test
Test: make RunSettingsRoboTests ROBOTEST_FILTER=com.android.settings.password
Change-Id: I86e294015354c0a6a6311441892a770503382d1f
3 files changed