How can I disable double opt-in?

How can I disable double opt-in?

Hi there! I have a single question, how can I disable double opt-in? 

I know that is't possible because it's mentioned here https://help.zoho.com/portal/community/topic/can-i-disable-double-opt-in-for-forms-or-api but I don't see this option in my web form as you can see in the attached image

Thanks.