Fix icon in bootstrap 3 'layout' example.

examples/layout-bootstrap3/templates/admin/index.html

@@ -12,6 +12,6 @@
     <p>
         This is done by overriding some of the built-in templates.
     </p>
-    <a class="btn btn-primary" href="/"><i class="icon-arrow-left icon-white"></i> Back</a>
+    <a class="btn btn-primary" href="/"><i class="glyphicon glyphicon-chevron-left"></i> Back</a>
 </div>
 {% endblock body %}