Remove unused assets, update old assets

chrome/browser/resources/help/help_content.css

 /* Copyright 2014 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.
  */
 
 #about-container {
   align-items: center;
   display: flex;
 }
 
@@ skipping 54 matching lines @@
 .help-page-icon {
   background-position: center;
   background-repeat: no-repeat;
   display: inline-block;
   height: 18px;
   vertical-align: middle;
   width: 18px;
 }
 
 #update-status-icon.up-to-date {
-  background-image: url(check_circle.svg);
+  background-image: url(../../../../ui/webui/resources/images/check_circle.svg);
   background-size: 18px;
 }
 
 #update-status-icon.working {
   background-image: url(chrome://resources/images/throbber.svg);
   background-size: 16px;
 }
 
 #update-status-icon.failed {
   background-image: url(chrome://resources/images/error.svg);
@@ skipping 55 matching lines @@
 }
 
 #regulatory-label-container {
   padding-top: 32px;
 }
 
 #regulatory-label {
   display: block;
   width: 330px;
 }