The Plesk is a commercial web hosting platform. The Plesk’s control panel allows a server administrator to set up new websites, reseller accounts, e-mail accounts, and DNS entries through a web-based interface. The following cli-linux command can be used to remove the specific subdomain from the specified domain.
plesk bin subdomain --remove -subdomains sample, forum -domain example.com
or
plesk bin subdomain -r -subdomains sample, forum -domain example.com