iOS ImageViewer: changed icon for a newer version (#2998)

* ios image viewer: changed icon for a newer version

* ios image viewer: renamed icon

examples/imageviewer/iosApp/iosApp/Assets.xcassets/AppIcon.appiconset/Contents.json

@@ -1,7 +1,7 @@
 {
   "images" : [
     {
-      "filename" : "image.png",
+      "filename" : "image_viewer_icon.png",
       "idiom" : "universal",
       "platform" : "ios",
       "size" : "1024x1024"