[FIX] mass_mailing: fix mailing count in stats button in campaign

Currently we are getting all records of mailing.mailing instead of
getting only records with mailing_type=mail. This bug was produced
by commit[1].

Now we have computed only that records which have mailing_type = mail,
So we can get perfect count in mail stats button in campaign.

commit[1] -> odoo/odoo@3f6625ef13

Task-2417993

closes odoo/odoo#76622

X-original-commit: 4f2924c5fcab672882ca78a9e6eb38b363d2d1b3
Signed-off-by: Thibault Delavallee (tde) <tde@openerp.com>

addons/mass_mailing/models/utm.py

@@ -47,7 +47,7 @@ class UtmCampaign(models.Model):
     def _compute_mailing_mail_count(self):
         if self.ids:
             mailing_data = self.env['mailing.mailing'].read_group(
-                [('campaign_id', 'in', self.ids)],
+                [('campaign_id', 'in', self.ids), ('mailing_type', '=', 'mail')],
                 ['campaign_id', 'ab_testing_enabled'],
                 ['campaign_id', 'ab_testing_enabled'],
                 lazy=False,