[FIX] account_edi: also send electronic document for the payments

When we want to send the invoice to the client, a hack was made in account_edi
to make sure that we put the XML of the electronic invoice formats as well, in
the case of web services such that the client has the XML we sent to the government.

For MX however, we also send the payment to the government.  However when we wanted
to send the confirmation about the different changes, we still needed to add the XML
manually before this fix.  Now it should be added manually even when manually composing
the mail to the customer with the payment receipt confirmation.  (but we hope it dies)

closes odoo/odoo#66728

Signed-off-by: Laurent Smet <smetl@users.noreply.github.com>