[FIX] point_of_sale: refresh when qty changed

- In the POS screen, select a product.
- Set the keyboard on "Price" mode
- Change the unit price
- Set the keyboard on "Qty" mode
- Change the qty

The product qty and the total price doesn't refresh until you go to the
payment screen.

We manually trigger a change when the quantity is updated.

opw-1855970

addons/point_of_sale/static/src/js/models.js

@@ -1405,6 +1405,7 @@ exports.Orderline = Backbone.Model.extend({
             this.set_unit_price(this.product.get_price(this.order.pricelist, this.get_quantity()));
             this.order.fix_tax_included_price(this);
         }
+        this.trigger('change', this);
     },
     // return the quantity of product
     get_quantity: function(){