When we investigate problems in developer’s apps by their request, we usually need access to the app and therefore we are added to these apps as developers. Apparently your app had some issue which I investigated and missed to delete myself from the app afterwards. You can either remove my entry from the app or if you provide the appId I can do that myself.
You can be sure that your data is safe, we do not use it in any way other than to investigate any problems if it’s needed. Also as you may already know, your data is still on our servers (if it’s Online or Managed version) so technically it’s anyway available to our dev team.