Remove code that check for dashboard feature.

- remove DashboardFeatureProvider.isEnabled() and all relating code
and tests.

Bug: 35764802
Test: make RunSettingsRoboTests
Change-Id: If7796677abc8904b7436525836d50cdef38e37a4

tests/robotests/src/com/android/settings/applications/AppInfoWithHeaderTest.java

@@ -72,7 +72,6 @@ public class AppInfoWithHeaderTest {
                 ShadowApplication.getInstance().getApplicationContext(),
                 mAppInfoWithHeader,
                 null);
-        when(mFactory.dashboardFeatureProvider.isEnabled()).thenReturn(true);
         when(mFactory.applicationFeatureProvider.newAppHeaderController(mAppInfoWithHeader, null))
                 .thenReturn(appHeaderController);
         mAppInfoWithHeader.onActivityCreated(null);