Update reference file for contributing guide test.

Author: domdfcoding

tests/test_files/test_contributing_/test_make_contributing_3_7_.html

@@ -14,8 +14,8 @@ <h2>Coding style</h2>
 <section id="automated-tests">
 <h2>Automated tests</h2>
 <p>Tests are run with <span class="docutils literal">tox</span> and <span class="docutils literal">pytest</span>.
-To run tests for a specific Python version, such as Python 3.6:</p>
-<pre><code>$<span class="w"> </span>tox<span class="w"> </span>-e<span class="w"> </span>py36</code></pre>
+To run tests for a specific Python version, such as Python 3.10:</p>
+<pre><code>$<span class="w"> </span>tox<span class="w"> </span>-e<span class="w"> </span>py310</code></pre>
 <p>To run tests for all Python versions, simply run:</p>
 <pre><code>$<span class="w"> </span>tox</code></pre>
 </section>