Fixed typo.

src/Avalonia.Controls.DataGrid/DataGrid.cs

@@ -1,5 +1,4 @@
-// (c) Copyright Microsoft Corporation.
+// This source is subject to the Microsoft Public License (Ms-PL).
-// This source is subject to the Microsoft Public License (Ms-PL).
 // Please see http://go.microsoft.com/fwlink/?LinkID=131993 for details.
 // All other rights reserved. 
 
@@ -767,7 +766,7 @@ namespace Avalonia.Controls
         /// <summary>
         /// ItemsProperty property changed handler.
         /// </summary>
-        /// <param name="e">AvaloniaPropertyChangedEventArgsdEventArgs.</param>
+        /// <param name="e">The event arguments.</param>
         private void OnItemsPropertyChanged(AvaloniaPropertyChangedEventArgs e)
         {
             if (!_areHandlersSuspended)