fix comment in typo based on PR

Microsoft.Toolkit.Uwp.UI.Controls.Input/TokenizingTextBox/TokenizingTextBox.cs

@@ -89,7 +89,7 @@ private void ItemsSource_PropertyChanged(DependencyObject sender, DependencyProp
                     }
                 }
 
-                // Add our text box at the end of items and set it's default value to our initial text, fix for #4749
+                // Add our text box at the end of items and set its default value to our initial text, fix for #4749
                 _currentTextEdit = _lastTextEdit = new PretokenStringContainer(true) { Text = Text };
                 _innerItemsSource.Insert(_innerItemsSource.Count, _currentTextEdit);
                 ItemsSource = _innerItemsSource;