[FIX] point_of_sale: ship later with multiple expense account

Current behavior:
If you had 2 products with different expense account and using real-time
inventory valuation, there was an error when validating the picking.
This was happening because move_vals we were trying to assign multiple
moves to one pos_order here https://github.com/odoo/odoo/blob/95cec6ea3daebce6491cc2a8a69d9688322989ba/addons/point_of_sale/models/stock_picking.py#L155



The account move is actually reserved for the invoicing of the order.
So we just need to remove that line.

Steps to reproduce:
- Create a product with expense account A
- Create a product with expense account B
- Make sure both products are set to real-time inventory valuation
- Activate ship later in the PoS
- Open the PoS and add both products to the order
- Validate the order with ship later and no invoice
- Close the PoS and try to validate the picking of the order.

opw-3428033

closes odoo/odoo#133301

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