Remove some dead code

DashboardCategory is no longer rendered in the dashboard ui

Bug: 33861822
Test: make RunSettingsRoboTests existing tests still pass
Change-Id: I0479967b0099f76f8c0c7894643d50b655de2892

src/com/android/settings/dashboard/DashboardAdapter.java

@@ -293,10 +293,6 @@ public class DashboardAdapter extends RecyclerView.Adapter<DashboardAdapter.Dash
             case R.layout.dashboard_header_spacer:
                 onBindHeaderSpacer(holder, position);
                 break;
-            case R.layout.dashboard_category:
-                onBindCategory(holder,
-                        (DashboardCategory) mDashboardData.getItemEntityByPosition(position));
-                break;
             case R.layout.dashboard_tile:
                 final Tile tile = (Tile) mDashboardData.getItemEntityByPosition(position);
                 onBindTile(holder, tile);