You can leave the stable if you are not a part of the stable anymore.
The owner of the stable would have to assign a new owner before being able to leave the stable.
Click here to learn how to assign a new owner.
To leave the stable you have to navigate to "Cancel subscription" through "Settings".
Use the "Leave stable" button.
For security you will have to confirm your decision by filling in your password, then you can leave the stable by using the "Leave stable" button.