Extension docs: Cleanup after there's only one version.

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

 <h1 class="page_title">chrome.experimental.* APIs</h1>
-{{^is_apps}}
-<div class="doc-family extensions">
-<p>
-Before you start, <strong>choose the right version of this page.</strong>
-You should read either:
-</p>
-
-<ul>
-  <li> <a href="http://code.google.com/chrome/extensions/trunk/experimental.html">Most recent experimental APIs</a>
-  <li> <a href="http://code.google.com/chrome/extensions/dev/experimental.html">Dev channel experimental APIs</a></li>
-</ul>
-
-<p>
-For information about browser versions such as
-Canary (bleeding edge) and the Dev channel, see
-<a href="http://www.chromium.org/getting-involved/dev-channel">Chrome Release Channels</a>.
-For details about channel-specific docs,
-see <a href="docs.html#versions">Doc versions</a>.
-</p>
-</div>
-{{/is_apps}}
 
 <h2 id="overview">
 List of APIs
 </h2>
 
 {{^is_apps}}
 <p class="doc-family extensions">
 We'd like your <a href="http://groups.google.com/a/chromium.org/group/chromium-extensions/topics">feedback</a>
 on the following experimental APIs:
 </p>
@@ skipping 39 matching lines @@
   {{^is_apps}}
   <li class="doc-family extensions">
     Make sure you're using either
     <a href="http://tools.google.com/dlpage/chromesxs">Canary</a>
     (which you can use at the same time as other Chrome channels) or the
 <a href="http://www.chromium.org/getting-involved/dev-channel">Dev channel</a>.
     Although the experimental APIs might work in other versions,
     we need your feedback on the latest incarnation of the APIs,
     which you can find in Canary and on the Dev channel.
   </li>
-  <li class="doc-family extensions">
-    Using either the
-    <a href="http://code.google.com/chrome/extensions/trunk/experimental.html">most recent API documentation</a> (if you're using Canary) or the
-    <a href="http://code.google.com/chrome/extensions/dev/experimental.html">API documentation for the Dev channel</a>,
-    write the code for your extension.
-  </li>
   {{/is_apps}}
   <li>
     Specify the "experimental"
     <a href="declare_permissions.html">permission</a>
     in your manifest, like this:
 <pre>
 "permissions": [
   <b>"experimental"</b>,
   ...
 ],
@@ skipping 33 matching lines @@
   {{/is_apps}}
 </ol>
 
 <h2 id="other">More APIs</h2>
 
 <p>
 For information on the standard APIs, see
 <a href="api_index.html">chrome.* APIs</a> and
 <a href="api_other.html">Other APIs</a>.
 </p>