Fix pip dependencies

Change-Id: I5c102f5fe4a509d64c4e0bc62a899dc738a8cbea

guides/how-to-contribute-to-this-documentation.rst

@@ -22,12 +22,15 @@ see :doc:`the beginning of our patch submission guide
 <how-to-submit-a-patch>` (TODO).
 
 If you want to preview your changes locally in your web browser, you
-need to install `Sphinx <https://www.sphinx-doc.org>`_.  You also need
-to install a markdown parser for Sphinx:
+need to install `Sphinx <https://www.sphinx-doc.org>`_,
+the `Read the Docs Sphinx theme
+<https://sphinx-rtd-theme.readthedocs.io/en/stable/>`_,
+and the `MyST Markdown parser
+<https://myst-parser.readthedocs.io/en/latest/index.html>`_.
 
 .. code-block:: bash
 
-   $ pip install --upgrade recommonmark
+   $ pip install --upgrade sphinx sphinx_rtd_theme myst_parser
 
 
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