Added prefix to enable intersphinx django link

Author: claudep

docs/quickstart.txt

@@ -6,8 +6,8 @@ To get started using the ``comments`` app, follow these steps:
 
 #. Install the comments app by running ``pip install django-contrib-comments``.
 
-#. :ref:`Enable the "sites" framework <enabling-the-sites-framework>` by adding
-   ``'django.contrib.sites'`` to :setting:`INSTALLED_APPS` and defining
+#. :ref:`Enable the "sites" framework <django:enabling-the-sites-framework>` by
+   adding ``'django.contrib.sites'`` to :setting:`INSTALLED_APPS` and defining
    :setting:`SITE_ID`.
 
 #. Install the comments framework by adding ``'django_comments'`` to