[FIX] purchase: fiscal position change must trigger a tax recomputation
[FIX] purchase: fiscal position change must trigger a tax recomputation

It applies the same behavior than in the Sales module.

opw-756556
Closes #18377

ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo