Add a bottom margin to the app header so that the scroll position is consistent.

Note that this is not going to look right until b/80433726 is fixed.

Bug: 80216430
Test: Manual
Change-Id: I90ec52ad3ff6c376648724ed38493157d89212fa
diff --git a/res/layout/app_grid_activity.xml b/res/layout/app_grid_activity.xml
index b1ff45d..72538a8 100644
--- a/res/layout/app_grid_activity.xml
+++ b/res/layout/app_grid_activity.xml
@@ -26,13 +26,14 @@
     <include
         layout="@layout/app_grid_activity_header"
         android:layout_width="match_parent"
-        android:layout_height="wrap_content" />
+        android:layout_height="wrap_content"
+        android:layout_marginBottom="@dimen/car_padding_4" />
 
     <androidx.car.widget.PagedListView
         android:id="@+id/apps_grid"
         android:layout_width="match_parent"
         android:layout_height="match_parent"
-        app:listContentTopOffset="@dimen/car_padding_4"
+        app:scrollBarTopMargin="0dp"
         app:dayNightStyle="auto"
         app:showPagedListViewDivider="false" />
 </LinearLayout>