DevTools: NetworkPanel: remove noop CSS.

Source/devtools/front_end/networkPanel.css

 /*
  * Copyright (C) 2006, 2007, 2008 Apple Inc.  All rights reserved.
  * Copyright (C) 2009 Anthony Ricaud <rik@webkit.org>
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
@@ skipping 44 matching lines @@
     position: absolute;
     top: 0;
     bottom: 0;
     left: 0;
     right: 0;
     width: auto;
     border: none;
     background: inherit;
 }
 
-.network.panel .data-grid th.sort-descending,
-.network.panel .data-grid th.sort-ascending {
-    background: white;
-}
-
 #network-views .network-item-view .tabbed-pane-header {
     flex: 0 0 31px;
     padding-top: 8px;
     padding-left: 13px;
     white-space: nowrap;
 }
 
 #network-views.small .network-item-view .tabbed-pane-header {
     flex-basis: 23px;
     padding-top: 0;
@@ skipping 71 matching lines @@
 
 .panel.network .split-view {
     flex: auto;
     position: relative;
 }
 
 .network-filters-header {
     flex: 0 0 23px;
     padding-right: 4px;
 }