Removed unused field from WicBitmapImpl

src/Windows/Avalonia.Direct2D1/Media/Imaging/WicBitmapImpl.cs

@@ -17,8 +17,7 @@ namespace Avalonia.Direct2D1.Media
     public class WicBitmapImpl : BitmapImpl
     {
         private readonly ImagingFactory _factory;
-
-        private SharpDX.Direct2D1.Bitmap _direct2D;
+        
 
         /// <summary>
         /// Initializes a new instance of the <see cref="WicBitmapImpl"/> class.
@@ -101,7 +100,6 @@ namespace Avalonia.Direct2D1.Media
         public override void Dispose()
         {
             WicImpl.Dispose();
-            _direct2D?.Dispose();
         }
 
         /// <summary>