[working-with] navigation, fix images

Author: conceptdev

WorkingWithNavigation/README.md

@@ -3,9 +3,9 @@ Working with Navigation
 
 This sample relates to the [Working with Navigation in Xamarin.Forms (1.3)](http://developer.xamarin.com/guides/cross-platform/xamarin-forms/working-with/navigation) doc.
 
-![screenshot](https://raw.githubusercontent.com/xamarin/xamarin-forms-samples/master/WorkingWithNativation/Screenshots/navigation-ios.png "Navigation")
+![screenshot](https://raw.githubusercontent.com/xamarin/xamarin-forms-samples/master/WorkingWithNavigation/Screenshots/navigation-ios.png "Navigation")
 
-![screenshot](https://raw.githubusercontent.com/xamarin/xamarin-forms-samples/master/WorkingWithNativation/Screenshots/navigation-android.png "Navigation")
+![screenshot](https://raw.githubusercontent.com/xamarin/xamarin-forms-samples/master/WorkingWithNavigation/Screenshots/navigation-android.png "Navigation")
 
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