There isn't a way for you to deactivate it from your side currently.
However if you request it, then I could deactivate your account for you. Though note that if you ever wanted to use the account later, you would have to ask for support again to get it reactivated.
Note that the only difference between an active and a deactivated account is whether you can login and receive e-mail notifications, and e-mail notifications can be disabled from your control panel, which negates any benefit to deactivating it.