Fix when GH `email-failure` action sends notification.

[bbannier]

In order to detect whether to send out a failure email we previously would check that the action conclusion contained certain statuses. This check seems to have been nonsensical as we only notified for benign failure reasons (the check would have made a little more sense if negated, but would have then also notified on successes).

With this patch we instead explicitly enumerate the failure conclusions to trigger on, see https://docs.github.com/en/webhooks/webhook-events-and-payloads#check_suite--check_suite-object for the full list of conclusions.