fix: change onsite tool icon to match the icons displayed at MeetEcho (ietf-tools#3574)

Author: rjsparks

ietf/templates/meeting/session_buttons_include.html

@@ -42,7 +42,7 @@
     {% if timeslot.location.onsite_tool_url %}
       <a class=""
         href="{{timeslot.location.onsite_tool_url|format:session }}"
-        title="Onsite tool"><span class="fa fa-fw fa-street-view"></span>
+        title="Onsite tool"><span class="fa fa-fw fa-lg fa-mobile"></span>
       </a>
     {% endif %}
     <!-- Audio stream -->