[FIX] purchase: Wrong Fiscal position in multicompany

Steps to reproduce:

 -Create company A
 -Create company B
 -Admin user with both companies but currently in company B
 -Create Demo user only with company B
 -Create fiscal position A to company A
 -Create fiscal position B to company B
 -Create vendor with fiscal position A with company A and the same vendor with fiscal position B in company B
 -Create product and add the vendor created before
 -Set like Create a draft purchase order
 -Logging with Demo user
 -Create sale order with one sale order line with route make to order
 -Validate sale order

Bug:

 The purchase order created by sale order had the fiscal position company A.

Closes #23561
opw:1825098