Fix menu resource not referring to showAsAction with app compat namespace

app/src/main/res/menu/activity_tutorial_slide.xml

@@ -1,8 +1,8 @@
-<menu xmlns:android="http://schemas.android.com/apk/res/android">
+<menu xmlns:android="http://schemas.android.com/apk/res/android"
+      xmlns:app="http://schemas.android.com/apk/res-auto">
 
     <!-- Adds an item to the list. -->
     <item android:id="@+id/action_previous"
         android:title="@string/action_previous"
-        android:showAsAction="ifRoom|withText" />
-
+        app:showAsAction="ifRoom|withText" />
 </menu>