[FIX] pos_self_order: show correct total in order widget

Part-of: odoo/odoo#138352

addons/pos_self_order/static/src/app/components/order_widget/order_widget.js

@@ -77,7 +77,10 @@ export class OrderWidget extends Component {
                 const qty = !lastChange ? currentQty : currentQty - lastChange.qty;
 
                 acc.count += qty;
-                acc.price += line.displayPrice * qty;
+                const subtotal = this.selfOrder.config.iface_tax_included
+                    ? line.price_subtotal_incl
+                    : line.price_subtotal;
+                acc.price += (subtotal / currentQty) * qty;
 
                 return acc;
             },

addons/pos_self_order/static/src/app/models/line.js

@@ -66,11 +66,6 @@ export class Line extends Reactive {
         });
     }
 
-    get displayPrice() {
-        // for the moment we use price with tax included but we should look at the config setup
-        return this.price_subtotal_incl;
-    }
-
     updateDataFromServer(data) {
         for (const key in data) {
             let updatedValue = data[key];