[FIX] website_sale: allow public user to print cart

Current behavior :
A public user couldn't print his cart because a 403 error is raised

Steps:
- Install eCommerce
- Go to the shop as a public user
- Process an order and payment
-  Click on "Print" button on order confirmation page

Note: 
Backport of 15.0 8ff6664c9dc98b7282c57b2859745bf1030aabc9

OPW-2753275

closes odoo/odoo#84906

Signed-off-by: Grazioso Andrea (agr) <agr@odoo.com>