Requesting a new certificate is probably the easiest and safest way.
If you really want to avoid it, you can also manually edit the renewal configuration files in /etc/letsencrypt/renewal/ and change the settings under [renewalparams]. Make a backup first, and test your changes with certbot renew --dry-run to make sure you didn’t break anything.
We also support changing that with certbot certonly --cert-name [yourcertname] --force-renewal -a webroot -w /your/webroot/directory, for example. (This will issue a new certificate in place of the old one while changing the authenticator.)