SeparatorMenuItems are not activatable, so SEPARATOR is a more
appropriate role than MENU_ITEM.
This is also what GTK3 does with GtkSeparatorMenuItem.
Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/3773>
(cherry picked from commit
eb98f88c7ea2a9a9b0462347d967b5d138d41227)
this.label = new St.Label({text: text || ''});
this.add_child(this.label);
this.label_actor = this.label;
+ this.accessible_role = Atk.Role.SEPARATOR;
this.label.connect('notify::text',
this._syncVisibility.bind(this));