[FIX] website_sale: copied line is linked with the original order

- Create a sale.order with a product with an optional product
- Confirm order A
- Copy this order A, a new order B is created
--> Issue: the new line of order B are linked with an line of order A

closes odoo/odoo#84206

X-original-commit: 8f07d9d1
Signed-off-by: Yannick Tivisse (yti) <yti@odoo.com>