Remove .html extension from links

chrome/common/extensions/docs/templates/articles/app_manifestVersion.html

 <h1>Manifest Version</h1>
 
 <p>
   Applications are simply bundles of resources, wrapped
-  up with a <a href="manifest.html"><code>manifest.json</code></a> file that
+  up with a <a href="manifest"><code>manifest.json</code></a> file that
   describes the package's contents. The format of this file is generally stable,
   but occasionally breaking changes must be made to address important issues.
   Developers should specify which version of the manifest specification their
   package targets by setting a <code>manifest_version</code> key in their
   manifests.
 </p>
 
 <h2 id="current-version">Current Version</h2>
 
 <p>
   Chrome App developers must currently specify
   <strong><code>'manifest_version': 2</code></strong>:
 </p>
 
 <pre data-filename="manifest.json">
 {
   ...,
   "manifest_version": 2,
   ...
 }
 </pre>
 
 <p>
   Manifest version 1 only applied to extensions and hosted apps, not
   Chrome Apps.  It
-  was <a href="../extensions/manifestVersion.html">deprecated</a> in
+  was <a href="../extensions/manifestVersion">deprecated</a> in
   Chrome 18.
 </p>