Update RulerControlExample.xaml.cs

Author: yanjinhuagood

src/WPFDevelopers.Samples.Shared/ExampleViews/RulerControlExample.xaml.cs

@@ -1,16 +1,4 @@
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
-using System.Windows;
-using System.Windows.Controls;
-using System.Windows.Data;
-using System.Windows.Documents;
-using System.Windows.Input;
-using System.Windows.Media;
-using System.Windows.Media.Imaging;
-using System.Windows.Navigation;
-using System.Windows.Shapes;
+using System.Windows.Controls;
 
 namespace WPFDevelopers.Samples.ExampleViews
 {