Update default.liquid

Author: RDL-ANU

_layouts/default.liquid

@@ -13,7 +13,7 @@
       <meta http-equiv="refresh" content="3; url={{ redirect }}">
     {% endif %}
     {% include head.liquid %}
-    {% include google_tag.html %}
+    {% include google_tag.liquid %}
   </head>
 
   <!-- Body -->