[FIX] point_of_sale: PaymentScreen not updated after pricelist changes

Current behavior:
After changing customer on the PaymentScreen, the pricelist could be
modified, but the PaymentScreen was not updated accordingly.

Steps to reproduce:
- Create 2 different products with different taxes.
- Create a pricelist with a discount on the 2 products.
- Create a coupon that apply a 100% discount on the order.
- Start a PoS session
- Add the 2 products to the order and apply the coupon.
- The order total is now 0€.
- Go on the PaymentScreen
- Change the customer
- The order should still be 0€, but it's not.

opw-3049098

closes odoo/odoo#108196

Signed-off-by: Joseph Caburnay (jcb) <jcb@odoo.com>