[1.5.x] Fixed #6234 -- Removed obsolete note about json and ensure_ascii

Thanks aaron at cellmap.ca for the report.
Backport of 4e8d952 from master.

docs/topics/serialization.txt

@@ -166,15 +166,6 @@ Notes for specific serialization formats
 json
 ^^^^
 
-If you're using UTF-8 (or any other non-ASCII encoding) data with the JSON
-serializer, you must pass ``ensure_ascii=False`` as a parameter to the
-``serialize()`` call. Otherwise, the output won't be encoded correctly.
-
-For example::
-
-    json_serializer = serializers.get_serializer("json")()
-    json_serializer.serialize(queryset, ensure_ascii=False, stream=response)
-
 Be aware that not all Django output can be passed unmodified to :mod:`json`.
 In particular, :ref:`lazy translation objects <lazy-translations>` need a
 `special encoder`_ written for them. Something like this will work::