fix typo in Examples (#8911)

Author: ABA2396

xml/System.Windows/EventManager.xml

@@ -166,7 +166,7 @@
    
   
 ## Examples  
- The following example adds a handler for <xref:System.Windows.UIElement.PreviewMouseLeftButtonDown>, calling <xref:System.Windows.EventManager.RegisterClassHandler%2A>.  
+ The following example adds a handler for <xref:System.Windows.UIElement.PreviewMouseRightButtonDownEvent>, calling <xref:System.Windows.EventManager.RegisterClassHandler%2A>.  
   
  :::code language="csharp" source="~/snippets/csharp/System.Windows/EventManager/RegisterClassHandler/class1.cs" id="Snippetstaticandregisterclasshandler":::
  :::code language="vb" source="~/snippets/visualbasic/VS_Snippets_Wpf/ClassHandling/visualbasic/sdksamplelibrary/class1.vb" id="Snippetstaticandregisterclasshandler":::