If you're the owner of a project or an admin of a Team, you can remove a project from a Team.
If you own the project, you can remove that project from the Team in Project Settings.
Go to Edit Project-->Settings-->For a Team and click "Edit Teams". Then, uncheck the Teams you want to remove the project from and save. The project will no longer be in the Team.
Note: If you co-own this project with others, the co-owners can add or remove the project from a Team without your permission.
If you're the admin of a Team, you can remove a project by unchecking it on the Projects dropdown on your Team page.