you cannot delete it, either you have to log on alternative email to accept the deletion and re-log in on original email to confirm the deletion with same IP address.
or
there's another long way, which is delete the whole email and wait for 9months, and register new one with exactly same ID.
Remember you must not Log in account during the duration of 9 months otherwise, it will be reactivated back to 0day + it will recover all old information including alternative email.