Change link to theme explorer

Author: tcbegley

docs/templates/theme-explorer.html

@@ -12,7 +12,7 @@
   </p>
   <p>
     This app only shows Bootstrap components. Check out the original
-    <a href="https://github.com/AnnMarieW/HelloDash">
+    <a href="https://hellodash.pythonanywhere.com/">
       Plotly Dash theme explorer app
     </a>
     made by