[FIX] account: outstanding payment not posted

- Create an invoice of 100 for partner A, validate
- Create the following journal entry:
  Bank, debit: 100
  Account Receivable, credit: 100
  => do not post the entry!
- Go to the invoice

The draft journal entry is proposed as an outstanding payment.

This should not be the case; only a posted journal entry should be
suggested.

opw-2082015

closes odoo/odoo#43573

Signed-off-by: oco-odoo <oco-odoo@users.noreply.github.com>