Fix lint warning in GridViewPager sample

app xmlns wasn't used, but lint also recommends changing it to
http://schemas.android.com/apk/res-auto had it been used.

Change-Id: Ib7e0fbf14414532fd9afe0e4475b9fc1f26370c7
diff --git a/wearable/wear/GridViewPager/Wearable/src/main/res/layout/activity_main.xml b/wearable/wear/GridViewPager/Wearable/src/main/res/layout/activity_main.xml
index 8da1474..8c077ab 100644
--- a/wearable/wear/GridViewPager/Wearable/src/main/res/layout/activity_main.xml
+++ b/wearable/wear/GridViewPager/Wearable/src/main/res/layout/activity_main.xml
@@ -14,7 +14,6 @@
      limitations under the License.
 -->
 <FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
-    xmlns:app="http://schemas.android.com/apk/res/com.example.android.wearable.gridviewpager"
     android:layout_width="match_parent"
     android:layout_height="match_parent" >