Resetting captcha keys is now easier with individual captcha reset keys option. You can find this on the bottom left side inside Settings > Captchas> Selected CAPTCHA.

Clicking on reset keys will open a confirmation modal, click reset to reset both site and secret keys for the captcha.

And that’s it, your keys are reset, and the captcha will be disabled automatically. Make sure to keep your secret keys safe for future use, since most captcha providers don’t show you these in the future.
Note: The “Reset Keys” option becomes available only once keys have been saved.