Deleting a team is permanent, and only the owner can do so. If you're not the team owner, you won't see the option to delete your team, and you'll need to contact your owner for help.
Go to Team page.
Click on Delete link.
Check mark all actions to confirm and finish deleting.
Note: History of all projects on the team will be erased, members on the projects will lose access, and all shared links will be inaccessible.