Update Doc/tools/templates/customsourcelink.html

Co-authored-by: Hugo van Kemenade <1324225+hugovk@users.noreply.github.com>

Author: StanFromIreland

Doc/tools/templates/customsourcelink.html

@@ -11,7 +11,7 @@ <h3>{{ _('This page') }}</h3>
       {% if language != "en" %}
       <li>
         <a href="https://github.com/python/python-docs-{{ language }}/blob/{{ version }}/{{ pagename }}.po?plain=1"
-           rel="nofollow">{{ _('Show Translation Source') }}</a>
+           rel="nofollow">{{ _('Show translation source') }}</a>
       </li>
       {% endif %}
     </ul>