This fix restores the ability to process partial refunds for Point of Sale orders. It matters because businesses can once again refund only part of a sale when needed, avoiding incorrect refund handling caused by unreliable order total calculations.

This reverts commit https://github.com/odoo/odoo/commit/7db2c4e760fa9ac1085602c258e737352bc7dcef to allow partial refunding of pos order as the total_amount is not correct anymore.

opw-3827876