Don't use intersphinx reference in the README.rst (pypa#1000)

Author: dukecat0

README.rst

@@ -6,8 +6,8 @@ http://packaging.python.org
 The "Python Packaging User Guide" (PyPUG) aims to be the authoritative resource on
 how to package and install distributions in Python using current tools.
 
-To follow the development of Python packaging, see the :doc:`Python
-Packaging Authority <pypa:index>`.
+To follow the development of Python packaging, see the `Python
+Packaging Authority <https://www.pypa.io/en/latest/>`_.
 
 Code of Conduct
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