[FIX] purchase: partner_bank_id is wrongly set up

How to reproduce the bug ?

- install the accounting, contacts and purchase apps
- create several companies and enable the checkboxes of all
  these companies
- create a new contact and add a bank account for each company
- switch to a company different than the first one
- create a request for quotations in the purchase apps and
  confirm it
- in the accounting app, create a new vendor bill and use the
  auto-complete field to select the RFQ created earlier.

The bug:

When you try to create a vendor bill from a request for quotations,
the recipient bank is wrongly chosen. Because of that, there will be
2 issues. The first one is when you want to create the bill from the
RFQ: you will get an error and the invoice won't be created. The second
one is when you create an invoice then use the auto-complete field. In
this case, there won't be any error but the recipient bank will
be wrong.

opw-2731264

closes odoo/odoo#84305

Signed-off-by: Adrien Minet <admi@odoo.com>
Signed-off-by: Steve Van Essche <svs@odoo.com>