Remove suggestion UI v1 codes.

- remove the check for feature flag for suggestion UI v2 and switch to
use the v2 codes.
- remove all code related to v1 of suggestion UI

Fixes: 70573674
Test: make RunSettingsRoboTests

Change-Id: I99ab318c1c0192508a9c5e9e708e86319120d55b

tests/robotests/src/com/android/settings/dashboard/DashboardSummaryTest.java

@@ -164,10 +164,4 @@ public class DashboardSummaryTest {
         mSummary.onCategoriesChanged();
         verify(mSummary).rebuildUI();
     }
-
-    @Test
-    public void onSuggestionDismissed_shouldNotRebuildUI() {
-        mSummary.onSuggestionDismissed(mock(Suggestion.class));
-        verify(mSummary, never()).rebuildUI();
-    }
 }