Fix VC list view template

Wrong header name.

phonebox_plugin/templates/phonebox_plugin/voice_circuit_list_view.html

@@ -10,7 +10,7 @@
         {% import_button 'plugins:phonebox_plugin:import_voice_circuits' %}
     {% endif %}
 </div>
-<h1>{% block title %}Numbers{% endblock %}</h1>
+<h1>{% block title %}Voice Circuits{% endblock %}</h1>
 <div class="row">
 	<div class="col-md-9">
         {% include 'utilities/obj_table.html' with bulk_delete_url="plugins:phonebox_plugin:voice_circuit_bulk_delete" bulk_edit_url="plugins:phonebox_plugin:voice_circuit_bulk_edit" %}