Removed unused reference. (#934)

Author: ezio-melotti

index.rst

@@ -261,4 +261,3 @@ Full Table of Contents
 .. _IronPython: https://ironpython.net/
 .. _Stackless: https://github.com/stackless-dev/stackless/wiki/
 .. _Issue tracker: https://github.com/python/cpython/issues
-.. _open pull requests: https://github.com/python/cpython/pulls?utf8=%E2%9C%93&q=is%3Apr%20is%3Aopen%20label%3A%22awaiting%20review%22