Update samples.

Samples/Server/Server_Retained_Messages_Samples.cs

@@ -1,3 +1,11 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+// ReSharper disable UnusedType.Global
+// ReSharper disable UnusedMember.Global
+// ReSharper disable InconsistentNaming
+
 using System.Text.Json;
 
 namespace MQTTnet.Samples.Server;