update data files link to segments4 in about

index.html

@@ -92,7 +92,7 @@
         </p>
         <p>
             <i>Data:</i> based on <a href="http://www.openstreetmap.org" target="_blank">OpenStreetMap</a>. It is usually updated once a week when a new Planet file is available, 
-            see dates of <a href="http://brouter.de/brouter/segments3/" target="_blank">data files</a>.
+            see dates of <a href="http://brouter.de/brouter/segments4/" target="_blank">data files</a>.
         </p>
         <p>
              <i><a href="https://github.com/nrenner/brouter-web#credits-and-licenses" target="_blank">Credits</a></i>,