Fix image example

Summary: Bundled images is ios only, legacy image was not present in android resources.

Reviewed By: javache

Differential Revision: D3930349

fbshipit-source-id: 663019351615b173621ef27dbf67ec595f8a590f

Examples/UIExplorer/js/ImageExample.js

@@ -612,7 +612,7 @@ exports.examples = [
     render: function() {
       return (
         <Image
-          source={require('image!LegacyImage')}
+          source={require('image!legacy_image')}
         />
       );
     },
@@ -645,6 +645,7 @@ exports.examples = [
         </View>
       );
     },
+    platform: 'ios',
   },
 ];