If your main goal is to not get USN reminders for your snap, you can simply
snapcraft close mysnap edge beta candidate stable (and any other tracks/branches where it might be published) and you will stop getting notifications. Check: Notifications for out of date stage-packages which states:
the service will examine snaps that have manifest.yaml files for their currently published channels/tracks
by closing the channels the snap becomes effectively unpublished.
As for removing the snap - there was the dreaded “trashcan” that effectively revoked a snap name and unpublished all uploads, but note that this has implications beyond just “deleting” the snap - it makes the name unusable forever for the previous owner, and releases the name again for registration by anybody else. Revocation is a non-recoverable operation, and the usual desktop metaphor of a trashcan led users to believe it was easily reversible.
Since these consequences were not very clear from just the icon, the trashcan was removed and we ask that people who want to have a snap name revoked request that operation in the forum, so we can (as I hopefully have done) explain the implications and get an informed decision from users.
You can read more about this in these two topics: How to delete snap and Deregistering snap name / regaining owner ship of revoked snap name from store.