demo: update the correct example link for the new demo

examples/example4-model-html-formatters.html

@@ -117,7 +117,7 @@ <h2>Demonstrates:</h2>
       </ul>
       <h2>View Source:</h2>
       <ul>
-          <li><A href="https://github.com/6pac/SlickGrid/blob/master/examples/example4-model-esm.html" target="_sourcewindow"> View the source for this example on Github</a></li>
+          <li><A href="https://github.com/6pac/SlickGrid/blob/master/examples/example4-model-html-formatters.html" target="_sourcewindow"> View the source for this example on Github</a></li>
       </ul>
     </div>
   </div>