Removes logic to disable gesture nav when default home app changes

Bug: 137197916
Test: Manual test with setting a 3P launcher as default
Test: make RunSettingsRoboTests ROBOTEST_FILTER=SystemNavigationGestureSettingsTest
Test: make RunSettingsRoboTests ROBOTEST_FILTER=SystemNavigationPreferenceControllerTest
Test: make RunSettingsRoboTests ROBOTEST_FILTER=RadioButtonPreferenceWithExtraWidgetTest
Change-Id: Id397cfa1c2439222aa21a7b7fe5f69818bf1fe97
4 files changed