Update tasks.py
Update tasks.py

Following https://docs.celeryproject.org/en/stable/internals/deprecation.html the importing of the celery task decorator needs to be updated for use with the current version of the celery package.
django-helpdesk/django-helpdesk,django-helpdesk/django-helpdesk,gwasser/django-helpdesk,gwasser/django-helpdesk,gwasser/django-helpdesk,django-helpdesk/django-helpdesk,gwasser/django-helpdesk,django-helpdesk/django-helpdesk