applets/kicker: drop sorted property in ItemListDialog

ItemListDialog forwards the source model's sorted property if set. This
was necessary when we filtered separators on sorted menus in the
frontend, but we now do it in the backend for better results since
d4ea56419a. The sorted property has no
more function now. Let's kill it.

applets/kicker/ItemListDialog.qml

@@ -57,8 +57,6 @@ Kicker.SubMenu {
         Kicker.FunnelModel {
             id: funnelModel
 
-            property bool sorted: sourceModel?.sorted ?? false
-
             Component.onCompleted: {
                 kicker.reset.connect(funnelModel.reset);
             }