Remove SplitViewPaneClosingEventArgs

src/Avalonia.Controls/SplitView/SplitViewPaneClosingEventArgs.cs

@@ -1,14 +0,0 @@
-using System;
-
-namespace Avalonia.Controls
-{
-    public class SplitViewPaneClosingEventArgs : EventArgs
-    {
-        public bool Cancel { get; set; }
-
-        public SplitViewPaneClosingEventArgs(bool cancel)
-        {
-            Cancel = cancel;
-        }
-    }
-}