Remove reference to permissions API from experimental page, it's no longer experimental.

chrome/common/extensions/docs/static/experimental.html

 <div id="pageData-name" class="pageData">chrome.experimental.* APIs</div>
 <div id="pageData-showTOC" class="pageData">true</div>
 
 <div class="doc-family extensions">
 <p>
 Before you start, <strong>choose the right version of this page.</strong>
 You should read either:
 </p>
 
 <ul>
@@ skipping 22 matching lines @@
 <ul>
   <li jsselect="listChromeAPIs(true);">
   <a jsvalues=".href: $this + '.html'" jscontent="$this"></a></li>
 </ul>
 
 <p class="doc-family extensions">
 Pay special attention to the following APIs,
 which we expect to finalize soon:
 <b>devtools</b>,
 <b>infobars</b>,
-<b>permissions</b>,
 For examples of using the experimental APIs, see
 <a href="samples.html#experimental">Samples</a>.
 </p>
 
 <p class="warning">
 <b>Caution:</b>
 Don't depend on these experimental APIs.
 They might disappear,
 and they <em>will</em> change.
 Also, the Chrome Web Store doesn't allow you to
@@ skipping 62 matching lines @@
   </li>
 </ol>
 
 <h2 id="other">More APIs</h2>
 
 <p>
 For information on the standard APIs that packaged apps can use, see
 <a href="api_index.html">chrome.* APIs</a> and
 <a href="api_other.html">Other APIs</a>.
 </p>