Disable creation of labels in Jira?
Based on the github reply I received, it looks only way is to allow it in Jira as it will spam same alert otherwise:


  Labels are how JIRAlert matches alerts to tickets. Without them, it
  would simply create a new ticket every time it gets called by
  Alertmanager for the same alert, i.e. once every few minutes.
  
  If I understand the error correctly, it looks like you'll have to
  enable labels for your JIRA project. I don't have admin access to a
  JIRA instance, so I can't tell you exactly how to do that.