You should not do this. The script check not only if the 2 passwords match but also if they comply with the password rules.
Even if you turn it off if password fields are send to the script they are checked on the server side.
What you can do is to set for username/email and password input fields "autocomplete" to off
https://developer.mozilla.org/en-US/docs/Web/Security/Securing_your_site/Turning_off_form_autocompletion