You can archive any app which is the same thing as deleting — only now you will have the ability to restore it later should you want to.

Archive an app
In the top-right corner of your Dashboard click Settings .
Choose Apps in the top navigation bar, and expand the app you want to archive.
Next to your app name, you can see the Archive button. Click it and confirm your action by clicking Archive again. You're done.
When you archive an app:
you can't access it on your Dashboard any more
users can't report bugs in this app
if you're on a paid plan, you won't be billed for it

Restore an app
When you archive an app, it goes to the Archived Apps page in your Settings. Should you decide you want to restore an app, just click the Restore button next to its name and it's active again. You can archive and restore an app as many times as you want.
When you restore an app:
it's visible on the Dashboard again
users can report bugs in this app again
if you're on a paid plan, you will be billed for it once again