[FIX] website_sale: do not copy last SO

- Create u1 as a portal user
- Connect as u1, add products to the cart
- Duplicate u1 (e.g. u2)
- Connect as u2

u2 retrieves the cart of u1.

opw-1847328

addons/website_sale/models/res_partner.py

@@ -7,4 +7,4 @@ from odoo import models, fields
 class ResPartner(models.Model):
     _inherit = 'res.partner'
 
-    last_website_so_id = fields.Many2one('sale.order', string='Last Online Sales Order')
+    last_website_so_id = fields.Many2one('sale.order', string='Last Online Sales Order', copy=False)