[FIX] mail: message_notify use the model and res_id arguments

Bug
===
The arguments model and res_id were declared on the method but never
used. This method was supposed to be callable from the model and not
from the records with those 2 parameters.

Make this possible.

Task-2599676

closes odoo/odoo#75497

Signed-off-by: Thibault Delavallee (tde) <tde@openerp.com>