Update create_global_jinja_loader docstring, #321.

flask/app.py

@@ -606,7 +606,7 @@ class Flask(_PackageBoundObject):
         """Creates the loader for the Jinja2 environment.  Can be used to
         override just the loader and keeping the rest unchanged.  It's
         discouraged to override this function.  Instead one should override
-        the :meth:`create_jinja_loader` function instead.
+        the :meth:`jinja_loader` function instead.
 
         The global loader dispatches between the loaders of the application
         and the individual blueprints.