[FIX] mail: Failed mail notification wrong title

opw-1921686

The failed mail notification group all the records of the same
model that failed to send an email.

Before this commit, the failed mail notification displayed as
title the name of the last record that failed to send an email.

Now, the notification displays as title the model name.

closes odoo/odoo#30134

addons/mail/static/src/js/models/mail_failure.js

@@ -83,7 +83,7 @@ var MailFailure = Class.extend(Mixins.EventDispatcherMixin, ServicesMixin, {
             documentModel: this._documentModel,
             id: 'mail_failure',
             imageSRC: this._moduleIcon,
-            title: this._recordName,
+            title: this._modelName,
         };
         return preview;
     },