Correct example to get Current Version

Filter for current version should be on value_name="CurrentVersion"

Author: simonsabin

docs/relational-databases/system-dynamic-management-views/sys-dm-server-registry-transact-sql.md

@@ -61,7 +61,7 @@ WHERE registry_key LIKE N'%SQLAgent%';
 ```  
 SELECT registry_key, value_name, value_data  
 FROM sys.dm_server_registry  
-WHERE registry_key = N'CurrentVersion';  
+WHERE value_name = N'CurrentVersion';  
 ```  
 
 ### D. Display the parameters passed to the instance of SQL Server during startup