[FIX] mail: Do not send log notes to customers

Issue

    - Install "CRM"
    - Create new lead
    - Set X to customer
    - Send a log note

    X receives log notes by mail

    Reproducible on Project and CRM

Cause

    The customer sends a list of partners who will receive an email
    even when it is a log note

Solution

    Send the list of partners only when it is an email and not a log note

opw-2369280

closes odoo/odoo#60836

Signed-off-by: Sébastien Theys (seb) <seb@odoo.com>