[FIX] calendar: use the correct model
[FIX] calendar: use the correct model

Getting the recurrent event in an order that make
sense for this model.
`self` is mail.message model, so this order can cause
crashes, since calendar.event and mail.message have
many different fields.

opw-743265

ygol/odoo,Elico-Corp/odoo_OCB,hip-odoo/odoo,ygol/odoo,Elico-Corp/odoo_OCB,hip-odoo/odoo,ygol/odoo,hip-odoo/odoo,Elico-Corp/odoo_OCB,Elico-Corp/odoo_OCB,hip-odoo/odoo,Elico-Corp/odoo_OCB,ygol/odoo,hip-odoo/odoo,ygol/odoo,ygol/odoo,Elico-Corp/odoo_OCB,ygol/odoo,hip-odoo/odoo