link to default docs URL from default app nav

default_app/index.html

@@ -149,7 +149,7 @@
     <span class="header-version vertical-middle"><script>document.write(process.versions.electron)</script></span>
 
     <div class="header-nav vertical-middle">
-      <a href="https://electron.atom.io/docs/latest">Docs</a>
+      <a href="https://electron.atom.io/docs">Docs</a>
       <a href="https://github.com/electron/electron">Repository</a>
       <a href="https://electron.atom.io/blog">Blog</a>
     </div>