Remove -Ofair option from celery worker
Remove -Ofair option from celery worker

In version 4.0 of celery, -Ofair became the default
scheduling strategy:
https://docs.celeryproject.org/en/latest/history/whatsnew-4.0.html?highlight=fair#ofair-is-now-the-default-scheduling-strategy

This appears to still be the case:
https://github.com/celery/celery/blob/5d68d781de807b4576cf5f574e5ba0aaf0d17388/celery/concurrency/asynpool.py#L80

Note, it took me a while to be certain of this as the documentation
for the celery CLI suggests a choice of `default` or `fair` which
isn't so useful as both of these are `fair`:
https://docs.celeryproject.org/en/latest/reference/cli.html#cmdoption-celery-worker-O

alphagov/notifications-api,alphagov/notifications-api