[1.2.X] Fixed #14118 -- Removed a reference to the "Python" serializer.

    ``json``    Serializes to and from JSON_ (using a version of simplejson_

                bundled with Django).

    ``python``  Translates to and from "simple" Python objects (lists, dicts,

                strings, etc.).  Not really all that useful on its own, but

                used as a base for other serializers.

    ``yaml``    Serializes to YAML (YAML Ain't a Markup Language). This

                serializer is only available if PyYAML_ is installed.

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