Removed the little sites doc

Sites now have some reference documentation in the page models reference

docs/reference/pages/index.rst

@@ -17,7 +17,6 @@ The presentation of your content, the actual webpages, includes the normal use o
     model_recipes
     editing_api
     streamfield
-    sites
     model_reference
     queryset_reference
     advanced_topics/privacy

docs/reference/pages/sites.rst

@@ -1,8 +0,0 @@
-.. _wagtail_site_admin:
-
-Sites
-=====
-
-Wagtail allows mapping a "site" (hostname or domain) to any node in the tree, using that node as the site's root. See :ref:`pages-theory`.
-
-Access this by going to "Settings" and then "Sites". To try out a development site, add a single site with the hostname ``localhost`` at port ``8000`` and map it to one of the pieces of content you have created.