[2.7] bpo-33503: Fix the broken pypi link in the source and the documentation (GH-6814). (GH-6905)

(cherry picked from commit 19177fbd5d6d9b29ccc302d65f9d9417ece082ce)

Co-authored-by: Stéphane Wirtel <stephane@wirtel.be>
diff --git a/Doc/installing/index.rst b/Doc/installing/index.rst
index cbbb882..9b89d08 100644
--- a/Doc/installing/index.rst
+++ b/Doc/installing/index.rst
@@ -39,9 +39,8 @@
   being installed system wide
 * ``virtualenv`` is a third party tools for creating virtual environments, it
   is defaults to installing ``pip`` into all created virtual environments.
-* the `Python Packaging Index <https://pypi.python.org/pypi>`__ is a public
-  repository of open source licensed packages made available for use by
-  other Python users
+* the `Python Packaging Index <https://pypi.org>`__ is a public repository of
+  open source licensed packages made available for use by other Python users
 * the `Python Packaging Authority
   <https://www.pypa.io/en/latest/>`__ are the group of
   developers and documentation authors responsible for the maintenance and