appMenu: Remove separator between "new window" and actions

We hide our own "New Window" item if the app itself includes a
"new-window" action. That means that the separator between the
built-in item and desktop actions introduces a small inconsistency
depending on whether a "New Window" item is provided by the desktop
action or ourselves. There's no good reason for that from a user's
perspective, so remove the separator.

Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/1948>

js/ui/appMenu.js

@@ -57,8 +57,6 @@ var AppMenu = class AppMenu extends PopupMenu.PopupMenu {
             Main.overview.hide();
         });
 
-        this.addMenuItem(new PopupMenu.PopupSeparatorMenuItem());
-
         this._actionSection = new PopupMenu.PopupMenuSection();
         this.addMenuItem(this._actionSection);