Bug 1074204 - Show correct android:summary text for sync. r=liuche

mobile/android/base/resources/xml/preferences.xml

@@ -13,7 +13,7 @@
 
     <org.mozilla.gecko.preferences.SyncPreference android:key="android.not_a_preference.sync"
                                                   android:title="@string/pref_sync"
-                                                  android:summary="@string/pref_category_customize_summary"
+                                                  android:summary="@string/pref_sync_summary"
                                                   android:persistent="false" />
 
     <PreferenceScreen android:title="@string/pref_category_customize"