The delete operation cannot continue because this snap-in is connected to the domain controller that is being deleted. To ...

The delete operation cannot continue because this snap-in is connected to the domain controller that is being deleted.  To remove Active Directory Domain Services, run the Remove Roles and Features Wizard in Server Manager, or run the Active Directory Domain Services Installation Wizard (DCPromo.exe) if the domain controller runs Windows Server 2008 R2 or earlier.