PDF: Tweak font-size and colors to more closely match other MD WebUI

chrome/browser/resources/pdf/elements/viewer-bookmark/viewer-bookmark.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. */
 
 #item {
   @apply(--layout-center);
   @apply(--layout-horizontal);
-  color: rgb(80, 80, 80);
   cursor: pointer;
-  font-size: 77.8%;
   height: 30px;
   position: relative;
 }
 
 #item:hover {
   background-color: rgb(237, 237, 237);
-  color: rgb(20, 20, 20);
 }
 
 paper-ripple {
   /* Allowing the ripple to capture pointer events prevents a focus rectangle
    * for showing up for clicks, while still allowing it with tab-navigation.
    * This undoes a paper-ripple bugfix aimed at non-Chrome browsers.
    * TODO(tsergeant): Improve focus in viewer-bookmark so this can be removed
    * (https://crbug.com/5448190). */
   pointer-events: auto;
 }
@@ skipping 15 matching lines @@
   width: 28px;
 }
 
 :host-context([dir=rtl]) #expand {
   transform: rotate(180deg);
 }
 
 :host([children-shown]) #expand {
   transform: rotate(90deg);
 }