set canonical url for 2.3 release

docs/docsite/_themes/srtd/layout.html

@@ -34,6 +34,9 @@
     <link rel="shortcut icon" href="{{ pathto('_static/' + favicon, 1) }}"/>
   {% endif %}
 
+  <link rel="canonical" href="https://docs.ansible.com/ansible/latest/{{ pagename }}.html"/>
+
+
   {# CSS #}
   <link href='https://fonts.googleapis.com/css?family=Lato:400,700|Roboto+Slab:400,700|Inconsolata:400,700' rel='stylesheet' type='text/css'>
   <link href='https://cdnjs.cloudflare.com/ajax/libs/font-awesome/4.0.3/css/font-awesome.min.css' rel='stylesheet' type='text/css'>