Remove custom layout for expandpreference.

It's no longer needed.
Test: manual
Change-Id: I704255ee217d1142ac81c738feef212224bae4e8

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

@@ -47,7 +47,6 @@ public class ExpandPreference extends Preference {
     }
 
     private void init() {
-        setLayoutResource(R.layout.expand_preference);
         setIcon(R.drawable.ic_arrow_down_24dp);
         setTitle(R.string.advanced_section_header);
         setOrder(999);