[FIX] base: correctly delete required many2one

In the transient model 'Change Password Wizard User', the many2one
`wizard_id` was not set as ondelete cascade even though this field was
required.

This was causing issues in the auto-vacuum cron if by chance this model
was cleaned up before the wizard ('Change Password Wizard').

Courtesy of @rco-odoo

Issue #813289

odoo/addons/base/models/res_users.py

@@ -954,7 +954,7 @@ class ChangePasswordUser(models.TransientModel):
     _name = 'change.password.user'
     _description = 'Change Password Wizard User'
 
-    wizard_id = fields.Many2one('change.password.wizard', string='Wizard', required=True)
+    wizard_id = fields.Many2one('change.password.wizard', string='Wizard', required=True, ondelete='cascade')
     user_id = fields.Many2one('res.users', string='User', required=True, ondelete='cascade')
     user_login = fields.Char(string='User Login', readonly=True)
     new_passwd = fields.Char(string='New Password', default='')