fix a help page CSS transition

chrome/browser/resources/help/help.css

 /* Copyright (c) 2012 The Chromium Authors. All rights reserved.
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 body {
   -webkit-user-select: text;
 }
 
 #overlay .page:not(.showing) {
@@ skipping 83 matching lines @@
 
 #more-info-expander {
   -webkit-padding-start: 0;
 }
 
 #more-info-container.visible {
   margin-bottom: 1.5em;
 }
 
 #more-info-container {
-  -webkit-transition: all 500ms linear;
+  -webkit-transition: all 200ms;
   height: 0;
   margin-bottom: 0;
   overflow: hidden;
 }
 
 #build-date-container.empty {
   visibility: hidden;
 }
 
 #channel-change-confirmation {
@@ skipping 21 matching lines @@
   background-size: 22px;
   vertical-align: top;
 }
 
 .channel-change-error-text {
   -webkit-margin-start: 4px;
   display: block;
   vertical-align: top;
   width: 240px;
 }