js: Use Gjs GTypeName computation for all classes

As per previous commit we can remove the explicit GTypeName definitions
and use gjs auto computation for all the GObject registered classes.

https://gitlab.gnome.org/GNOME/gnome-shell/merge_requests/790

js/ui/status/network.js

@@ -1591,9 +1591,8 @@ var DeviceCategory = class extends PopupMenu.PopupMenuSection {
     }
 };
 
-var NMApplet = GObject.registerClass({
-    GTypeName: 'Network_Indicator'
-}, class Indicator extends PanelMenu.SystemIndicator {
+var NMApplet = GObject.registerClass(
+class Indicator extends PanelMenu.SystemIndicator {
     _init() {
         super._init();