Add missing speaker name

TODO: Extract and use a Speaker class with a getName() method.

source/_includes/session-speakers.html.twig

@@ -4,7 +4,7 @@
   {% for speaker in speakers %}
     <li>
       <a href="{{ speaker.url }}">
-        {{ speaker.name }}
+          {{ speaker.title }}
       </a>
     </li>
   {% endfor %}