Drop mention of Python 2 from index page

Author: pradyunsg

docs/html/index.rst

@@ -23,11 +23,6 @@ Please take a look at our documentation for how to install and use pip:
    :ref:`Resolver changes 2020`. We want your input, so `sign up for
    our user experience research studies`_ to help us do it right.
 
-.. warning::
-
-   pip 21.0, in January 2021, will remove Python 2 support, per pip's
-   :ref:`Python 2 Support` policy. Please migrate to Python 3.
-
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 * `Issue tracking`_