Remove obsolete comments

src/Avalonia.Controls.DataGrid/DataGridBoundColumn.cs

@@ -51,10 +51,9 @@ namespace Avalonia.Controls
                         {
                             if (binding.Mode == BindingMode.OneWayToSource)
                             {
-                                throw new InvalidOperationException("DataGridColumn doesn't support BindingMode.OneWayToSource");
+                                throw new InvalidOperationException("DataGridColumn doesn't support BindingMode.OneWayToSource. Use BindingMode.TwoWay instead.");
                             }
 
-                            // Force the TwoWay binding mode if there is a Path present.  TwoWay binding requires a Path.
                             if (!String.IsNullOrEmpty(binding.Path) && binding.Mode == BindingMode.Default)
                             {
                                 binding.Mode = BindingMode.TwoWay;