Remove .html extension from links

chrome/common/extensions/docs/templates/articles/manifest/manifest_version.html

 <h1 id="manifest_version">Manifest Version</h1>
 
 <p>
 One integer specifying the version of the manifest file format your package
 requires. As of Chrome 18, developers <em>should</em> specify <code>2</code>
 (without quotes) to use the format as described by this document:
 </p>
 
 <pre data-filename="manifest.json">
 "manifest_version": 2
 </pre>
 
 <p>
 Consider manifest version 1 <em>deprecated</em> as of Chrome 18. Version 2 is
 not yet <em>required</em>, but we will, at some point in the not-too-distant
 future, stop supporting packages using deprecated manifest versions. Extensions,
 applications, and themes that aren't ready to make the jump to the new manifest
 version in Chrome 18 can either explicitly specify version <code>1</code>, or
 leave the key off entirely.
 </p>
 
 <p>
 The changes between version 1 and version 2 of the manifest file format are
-described in detail in <a href="http://developer.chrome.com/extensions/manifestVersion.html">the
+described in detail in <a href="http://developer.chrome.com/extensions/manifestVersion">the
 <code>manifest_version</code> documentation.</a>
 </p>
 
 <p class="caution">
   Setting <code>manifest_version</code> 2 in Chrome 17 or lower is not
   recommended. If your extension needs to work in older versions of Chrome,
   stick with version 1 for the moment. We'll give you ample warning before
   version 1 stops working.
 </p>