[FIX] sale_order_currency_rate : Change curency_rate calculation

[dalonsofl]

Module

sale_order_currency_rate

Describe the bug

The currency rate applied is not correct and the value in report is incorrect too

To Reproduce

1. Create a sale order and confirm
2. Check the value in sale report

(image from runboat OCA)

Instead of divining by the unit per USD is using the USD per unit and the value is incorect. Because this reason, the best option is using the base odoo calculation of currency_rate.

Affected versions:

16.0