You can uninstall a Digital Certificate from within your Control Panel provided by r2.
To Uninstall a Digital Certificate
cPanel Linux Web Hosting Packages
If you have purchased a cPanel Linux Web Hosting package with r2, then follow the below mentioned process:
Login to your Control Panel, Search for the domain name for which you have purchased this Hosting Order and go to the Order Information view. See details
Click the Manage Web Hosting link.
Click the SSL/TLS Manager under Security. See details