Please ignore the previous message. This is being fixed by using following stored procedure.
DECLARE @instance_id int;
SELECT @instance_id = mi.instance_id
FROM msdb.dbo.sysutility_ucp_managed_instances AS mi
WHERE mi.instance_name = 'ComputerName\InstanceName';
EXEC msdb.dbo.sp_sysutility_ucp_remove_mi @instance_id;
EXEC msdb.dbo.sp_sysutility_mi_remove;