[FIX] mail: no default alias owner

Before this change aliases were assigned to the user creating them

The purpose was originally to reduce the number of records created by
odoobot however this leads to unexpected
behavior for the users who just wanted to create an alias without fuss

We make remove the default user such that any automated record
modification/creation will be applied by root instead of some
arbitrary user.

task-3383275

X-original-commit: 3edf18168b92545fc29e078a155494f2781adff6
Part-of: odoo/odoo#130798

addons/mail/models/mail_alias.py

@@ -42,7 +42,7 @@ class Alias(models.Model):
                                       # hack to only allow selecting mail_thread models (we might
                                       # (have a few false positives, though)
                                       domain="[('field_id.name', '=', 'message_ids')]")
-    alias_user_id = fields.Many2one('res.users', 'Owner', default=lambda self: self.env.user,
+    alias_user_id = fields.Many2one('res.users', 'Owner',
                                     help="The owner of records created upon receiving emails on this alias. "
                                          "If this field is not set the system will attempt to find the right owner "
                                          "based on the sender (From) address, or will use the Administrator account "