Merge pull request #899 from am11/feature/build/net5.0

Delete using WindowsRuntime from unit test

UnitTests/PosTests.cs

@@ -4,7 +4,6 @@ using System.ComponentModel;
 using System.Data;
 using System.IO;
 using System.Linq;
-using System.Runtime.InteropServices.WindowsRuntime;
 using Terminal.Gui;
 using Xunit;