[FIX] account: do not subscribe commercial partner

- Create a partner which is a company
- Add a contact
- Create an invoice for the contact, post it

Both the contact and the company are set as followers of the invoice.

Only the contact should be, there is no reason to make the company
follower too.

opw-2179084

closes odoo/odoo#44474

Signed-off-by: Nicolas Martinelli (nim) <nim@odoo.com>