remove dead link to skills matter (#205)

Author: graingert

index.html

@@ -16,7 +16,6 @@ <h2>Links</h2>
         <li><a href="https://twitter.com/djangolondon">Twitter</a></li>
         <li><a href="https://www.linkedin.com/company/djangolondon">LinkedIn</a></li>
         <li><a href="https://www.youtube.com/channel/UCNfEKvjjUemcg4wbb3cO5og">YouTube</a></li>
-        <li><a href="https://skillsmatter.com/groups/10546-london-django-meetup-group">Skills Matter</a></li>
         <li><a href="https://github.com/djangolondon/">Github</a></li>
     </ul>