Remove gray line in the new user dialog and remove margin.

chrome/browser/resources/options/manage_profile_overlay.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. */
 
 #manage-profile-overlay {
   width: 612px;
 }
 
 .profile-icon-grid-item {
   height: 31px;
@@ skipping 43 matching lines @@
   max-height: 0;
   padding: 0 10px;
 }
 
 #create-profile-icon-grid,
 #manage-profile-icon-grid {
   background-color: rgba(255, 255, 255, 0.75);
   padding: 2px;
 }
 
-/* Adds a grey horizontal line below content area.  */
-#create-profile-content::after,
-#manage-profile-content::after {
-  background: #c0c0c0;
-  content: '';
-  display: block;
-  height: 1px;
-  margin-top: 25px;
-  width: 100%;
-}
-
 :-webkit-any(#create-profile-content, #manage-profile-content) >
     :not(:last-child) {
   margin-bottom: 10px;
 }
 
 :-webkit-any(#create-profile-content, #manage-profile-content) >
     :not(:first-child) {
   margin-top: 10px;
 }
 
@@ skipping 33 matching lines @@
 
 #create-profile-managed-not-signed-in {
   color: #999;
 }
 
 #create-profile-managed-not-signed-in-label,
 #create-profile-managed-account-details-out-of-date-label {
   white-space: pre-wrap;
   word-wrap: break-word;
 }