[FIX] HELPDESK: Fixed edit ticket after deadline for users with permission and moved clean from models to form (#949)

helpdesk/models.py

@@ -130,13 +130,6 @@ class Ticket(HorillaModel):
         verbose_name = _("Ticket")
         verbose_name_plural = _("Tickets")
 
-    def clean(self, *args, **kwargs):
-        super().clean(*args, **kwargs)
-        deadline = self.deadline
-        today = datetime.today().date()
-        if deadline < today:
-            raise ValidationError(_("Deadline should be greater than today"))
-
     def get_raised_on(self):
         obj_id = self.raised_on
         if self.assigning_type == "department":