docs: Do not autodoc private members any longer. The need really went away with the separation of BackendControllers and BackendProviders

docs/autodoc_private_members.py

@@ -1,10 +0,0 @@
-def setup(app):
-    app.connect('autodoc-skip-member', autodoc_private_members_with_doc)
-
-def autodoc_private_members_with_doc(app, what, name, obj, skip, options):
-    if not skip:
-        return skip
-    if (name.startswith('_') and obj.__doc__ is not None
-            and not (name.startswith('__') and name.endswith('__'))):
-        return False
-    return skip

docs/conf.py

@@ -25,7 +25,7 @@ import mopidy
 
 # Add any Sphinx extension module names here, as strings. They can be extensions
 # coming with Sphinx (named 'sphinx.ext.*') or your custom ones.
-extensions = ['sphinx.ext.autodoc', 'autodoc_private_members',
+extensions = ['sphinx.ext.autodoc',
     'sphinx.ext.graphviz', 'sphinx.ext.inheritance_diagram',
     'sphinx.ext.extlinks', 'sphinx.ext.viewcode']