Update use-managed-identity.md

Added clearification about PrincipalID as suggested by Saurya

Author: TomGeske

articles/aks/use-managed-identity.md

@@ -55,7 +55,7 @@ A successful cluster creation using managed identities contains this service pri
 ```
 
 > [!NOTE]
-> For creating and using your own VNet, static IP address, or attached Azure disk where the resources are outside of the MC_* resource group, use the PrincipalID of the cluster to perform a role assignment. For more information on role assignment, see [Delegate access to other Azure resources](kubernetes-service-principal.md#delegate-access-to-other-azure-resources).
+> For creating and using your own VNet, static IP address, or attached Azure disk where the resources are outside of the MC_* resource group, use the PrincipalID of the cluster System Assigned Managed Identity to perform a role assignment. For more information on role assignment, see [Delegate access to other Azure resources](kubernetes-service-principal.md#delegate-access-to-other-azure-resources).
 
 Finally, get credentials to access the cluster: