Fixed #26637 -- Removed obsolete note in docs/internals/contributing/writing-documentation.txt

To actually build the documentation locally, you'll currently need to install

Sphinx -- ``pip install Sphinx`` should do the trick.

.. note::

    Building the Django documentation requires Sphinx 1.0.2 or newer. Sphinx

    also requires the Pygments__ library for syntax highlighting; building the

    Django documentation requires Pygments 1.1 or newer (a new-enough version

    should automatically be installed along with Sphinx).

__ http://pygments.org

Then, building the HTML is easy; just ``make html`` (or ``make.bat html`` on

Windows) from the ``docs`` directory.