Files.app: Remove separator below “Files” in left nav.

chrome/browser/resources/file_manager/css/file_manager.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. */
 
 html {
   height: 100%;
 }
 
 html.col-resize * {
   cursor: col-resize !important;
@@ skipping 256 matching lines @@
 }
 
 body[new-ui] .dialog-sidebar-header #app-name {
   -webkit-margin-start: 15px;
   color: #303030;
   font-size: 130%;
 }
 
 body[new-ui] .dialog-sidebar-contents {
   -webkit-box-flex: 1;
-  border-top: 1px solid rgb(210, 210, 210);
   display: -webkit-box;
   position: relative;
 }
 
 body[new-ui] .dialog-sidebar-footer {
   -webkit-box-flex: 0;
   display: -webkit-box;
 }
 
 /* A vertical splitter between the roots list and the file list. It is actually
@@ skipping 2091 matching lines @@
 body[new-ui] #iframe-drag-area {
   -webkit-app-region: drag;
   height: 45px;
   left: 64px;
   position: absolute;
   right: 70px;
   top: 0;
   width: auto;
   z-index: 101;
 }