DevTools: remove hover effect from panel selector until migration to material look.

Source/devtools/front_end/components/inspectorViewTabbedPane.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.
  */
 
 .tabbed-pane-header {
     background-color: #f3f3f3;
     flex: 0 0 27px;
     overflow: visible;
 }
 
-.tabbed-pane-header-tab:hover {
-    background-color: rgba(105, 105, 105, 0.1) !important;
-}
-
 .tabbed-pane-header-tab,
 .tabbed-pane-header-tab.selected {
     height: 26px;
     margin: 0;
     background: none;
     border: none;
     border-left: 2px solid transparent;
     border-right: 2px solid transparent;
     padding: 0 6px;
 }
 
 .tabbed-pane-header-tab {
     color: #5a5a5a;
 }
 
 .tabbed-pane-header-tab.selected {
     color: #333;
     border-width: 0 2px 0 2px;
     -webkit-border-image: url(Images/toolbarItemSelected.png) 0 2 0 2;
 }