DevTools: Remove step into selection experiment

Source/devtools/front_end/inspector.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 2279 matching lines @@
     bottom: 0;
     left: 0;
     right: 0;
 }
 
 .source-frame-eval-expression {
     outline: 1px solid rgb(163, 41, 34);
     background-color: rgb(255, 255, 194);
 }
 
-.source-frame-stepin-mark {
-    cursor: pointer;
-    text-decoration: underline;
-}
-
-.source-frame-stepin-mark-highlighted {
-    font-weight: 800;
-    cursor: pointer;
-    text-decoration: underline;
-}
-
 .workers-list {
     list-style: none;
     margin: 0;
     padding: 0;
 }
 
 .resource-content-unavailable {
     color: rgb(50%, 50%, 50%);
     font-style: italic;
     font-size: 14px;
@@ skipping 524 matching lines @@
 }
 
 .root-view > .split-view > .split-view-sidebar {
     position: relative;
 }
 
 select.drop-down-menu {
     border: none;
     -webkit-appearance: none;
 }