[FIX] account: auto-complete apply the correct currency rate

Steps to reproduce:
- enable multi currency in settings
- set different rates for multiple days
- create a vendor bill in a different currency
- create a second vendor bill
- fill the second bill using auto complete from the first one

Bug:
the correct currency rate isn't applied unless date is changed when
the source is a vendor bill not a purchase order

Fix:
update currency rate after adding a line with a different currency

opw-2890210

closes odoo/odoo#99640

Signed-off-by: Grazioso Andrea (agr) <agr@odoo.com>