Add missing using

Author: josesimoes

Azure.Devices.DeviceClient/TwinUpdateEventArgs.cs

@@ -1,6 +1,7 @@
 // Copyright (c) Microsoft. All rights reserved.
 // Licensed under the MIT license. See LICENSE file in the project root for full license information.
 
+using nanoFramework.Azure.Devices.Client;
 using System;
 
 namespace nanoFramework.Azure.Devices.Shared