[MD settings] icon color and sizing centralized

chrome/browser/resources/settings/people_page/user_list.css

 /* Copyright 2015 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. */
 
-.clear-icon {
-  color: #6e6e6e;
-}
-
-.clear-icon::shadow iron-icon {
-  height: 18px;
-  width: 18px;
-}
-
 .soft-border {
   border: 1px solid #c4c4c4;
   border-radius: 2px;
 }
 
 .user {
   -webkit-padding-end: 8px;
   -webkit-padding-start: 20px;
   font-size: 0.75em;
   height: 34px;
 }
 
 .user:hover {
   background-color: #f0f0f0;
 }
 
 .user-list {
   border: 1px solid gray;
   height: 160px;
   overflow-y: auto;
   padding: 10px 0;
 }