Email verification can’t be disabled. You might not understand why, but you actually want and need email address verification.
Email is central to Discourse. Email addresses are considered as personally identifying information. You have a legal responsibility to verify that the address is owned by the user in question before storing it in your database.
If a user were to enter the wrong email address either accidentally (or intentionally) you would otherwise end up sending email address to a user who didn’t consent to receive such messages. If your mail domain ends up being reported for unsolicited emails you will find yourself quickly blocked by many of the larger email services.
Discourse will remove any accounts with unverified addresses to protect you from any data protection liability.