[FIX] survey: prevent certification email from being sent twice
[FIX] survey: prevent certification email from being sent twice

Purpose
=======

The certification email template had both "email_to" and "partner_to" fields set
and that implied the mail being sent twice.

This commit removes the "partner_to" field to fix it.
ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo