How to clean up servers demoted on Active Directory Sites and Services
1.
%SystemRoot%\system32\dssite.msc
%SystemRoot%\system32\dssite.msc
2.
Sites --> Default-First-Site-Name --> Servers
Sites --> Default-First-Site-Name --> Servers
3.
Right click the server that has been already demoted
Delete
Right click the server that has been already demoted
Delete
References
Clean up server metadata using Active Directory Sites and Services
Update