Code error in serialization docs

[Jared Forsyth]

Under ​serialization of natural keys, the following code is given as an example:

serializers.serialize([book1, book2], format='json', indent=2, use_natural_keys=True)

this throws an exception, as the non-kw arguments for serialize are [format, data]. This should be changed to

serializers.serialize('json', [book1, book2], indent=2, use_natural_keys=True)

the attached patch does this.

[Russell Keith-Magee]

(In [13530]) Fixed #13661 -- Corrected example in the serialization docs. Thanks to jabapyth for the report.

[Russell Keith-Magee]

(In [13536]) [1.2.X] Fixed #13661 -- Corrected example in the serialization docs. Thanks to jabapyth for the report.

Backport of r13530 from trunk.