Merge pull request jupyter#487 from jupyter/voila-img-fix

Correct the image used for the Voila block

Author: Carreau

index.html

@@ -108,7 +108,7 @@
   description: Voilà helps communicate insights by transforming notebooks into secure, stand-alone web applications that you can customize and share.
   image:
     alt: examples of Voilà dashboards
-    src: assets/architectureicon2.svg
+    src: assets/voilapreview.png
   buttons:
   - class:
     href: try