[sylius] cannot delete product, product in use

1. you should delete all orders, where contains product needs to delete.
2. remove all carts where, where remains this product. You can do it with php bin/console sylius:remove-expired-carts . If you need to remove all carts for all days, add parameter sylius_order.cart_expiration_period: 0  to app/config/config.yml and rerun previous command again.