Obsolete PinNumberingScheme

Let's see what breaks

Author: krwq

src/System.Device.Gpio/System/Device/Gpio/PinNumberingScheme.cs

@@ -1,11 +1,13 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
+namespace System;
 namespace System.Device.Gpio;
 
 /// <summary>
 /// Different numbering schemes supported by GPIO controllers and drivers.
 /// </summary>
+[Obsolete]
 public enum PinNumberingScheme
 {
     /// <summary>