Remove placeholder summary text in auto-rotate preference

- Remove the %s from xml and set it in code instead.
- This is hack to make search stop display %s. It's fixed properly in
  master but we don't want to cherry-pick the master change because of its
  size and risk.

Bug: 36101902
Test: rerun robotests
Change-Id: I0e03957532b265c15d5cc0754396aea26e5cd8a1
Merged-In: If42cceb74296814311eb0eff8e26b4a48a1c4d29

res/xml/display_settings.xml

@@ -59,7 +59,7 @@
 
     <DropDownPreference
         android:key="auto_rotate"
-        android:summary="%s"
+        android:summary="@string/summary_placeholder"
         android:title="@string/display_auto_rotate_title" />
 
     <Preference