Remove redundant json import.

docs/user/quickstart.rst

@@ -238,7 +238,6 @@ For example, the GitHub API v3 accepts JSON-Encoded POST/PATCH data::
 Instead of encoding the ``dict`` yourself, you can also pass it directly using
 the ``json`` parameter (added in version 2.4.2) and it will be encoded automatically::
 
-    >>> import json
     >>> url = 'https://api.github.com/some/endpoint'
     >>> payload = {'some': 'data'}