[FIX] account: right accounts in account group

Steps to reproduce:

- Create an account group for a range for example from 100000 to 200000
- Now edit the group to have a range from 100000 to 150000

Issue:

The accounts with code > 150000 are still in the account group

Solution

Adding an other intermediary table to the query in order to take into
account the accounts which have no group_id

opw-2695533

closes odoo/odoo#81475

Signed-off-by: Laurent Smet <las@odoo.com>