Please follow the steps to remove the Let's Encrypt SSL Certificate:
First take a backup of letsencrypt directory under /etc -
I deleted the ‘no longer needed domains’ in the three folders…
First take a backup of letsencrypt directory under /etc -
sudo cp -r /etc/letsencrypt/ /etc/letsencrypt.backup
rm -rf /etc/letsencrypt/live/${DOMAIN}
rm -rf /etc/letsencrypt/renewal/${DOMAIN}.conf
rm -rf /etc/letsencrypt/archive/${DOMAIN}