Remove ‘(all networks)’ from settings label

I don’t think we need to say (all networks) in the header. The real
benefit of this change is forcing the platform admin person making the
change to explicitly give their choice of network.

And by not putting it in the label we don’t have future users from other
organisations wondering if there’s some option other than ‘all networks’
they need to think about.

app/templates/service_navigation.html

@@ -23,9 +23,7 @@
     {% else %}
     <span class="navigation-service-type navigation-service-type--{{broadcast_channel}} {{margin_class}}">{{ broadcast_channel|title }}
     {% endif %}
-    {% if allowed_broadcast_provider == "all" %}
-      (all networks)
-    {% else %}
+    {% if allowed_broadcast_provider != "all" %}
       ({{ allowed_broadcast_provider|format_mobile_network }})
     {% endif %}
   {% endif %}