Bug 310271: Remove 'for originating site only' checkbox docs. r=jeff

browser/locales/en-US/chrome/help/prefs.xhtml

@@ -205,12 +205,6 @@ Contributors:
     By default images are loaded on web pages. Uncheck this &pref.singular;
     to disable images completely.</p>
 
-  <ul>
-    <li><em>for the originating web site only</em><br/>
-      Enabling this &pref.singular; will make sure that only images located at
-      the current web site are loaded.</li>
-  </ul>
-
   <p>Depending on if you enable images, you can change which sites are
     blocked or which sites can load images by clicking <em>Exceptions</em>.
     Enter the site you want to allow/deny images from and click