Remove .html extension from links

chrome/common/extensions/docs/templates/intros/notifications.html

 <p class="note">
 <b>Note: </b>
 This API is currently available on ChromeOS, Windows, and Mac.
 </p>
 
 <h2 id="usage">Usage</h2>
 
 <p>
 To use this API,
 call the $(ref:notifications.create) method,
@@ skipping 13 matching lines @@
 </p>
 
 <p>
 All template types
 (<code>basic</code>, <code>image</code>, and <code>list</code>)
 must include a notification <code>title</code> and <code>message</code>,
 as well as an <code>iconUrl</code>, which is a link to a small icon that
 is displayed to the left of the notification message. The <code>image</code>
 template type also includes an <code>imageUrl</code>, which is a link to
 an image that is previewed within the notification.
-Due to a strict <a href="contentSecurityPolicy.html">Content Security Policy</a>
+Due to a strict <a href="contentSecurityPolicy">Content Security Policy</a>
 in Chrome Apps, these URLs must point to a local resource or use a
-<a href="app_external.html">data URL</a>.
+<a href="app_external">data URL</a>.
 </p>
 
 <p>
 Here's an example of a <code>basic</code> template:
 </p>
 
 <pre>
 var opt = {
   type: "basic",
   title: "Primary Title",
@@ skipping 28 matching lines @@
 
 <p>
 All notifications can include event listeners and event handlers
 that respond to user actions.
 For example,
 you can write an event handler to respond to an
 $(ref:notifications.onButtonClicked) event.
 </p>
 
 <p>Consider including event listeners and handlers within the
-  <a href="app_lifecycle.html#create_event_page">event page</a>,
+  <a href="app_lifecycle#create_event_page">event page</a>,
 so that notifications can pop-up even when the app or extension isn't running.
 </p>