Remove dead code for system VK.

ui/keyboard/resources/main.css

-/*
- Copyright (c) 2013 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.
-*/
-
-@font-face {
-  font-family: roboto-bold;
-  src: url(roboto_bold.ttf);
-}
-
-/**
- * TODO(rsadam@): Remove all these rules once we switch to native
- * shadow dom.
- */
-kb-keyboard.ctrl-active kb-modifier-key[char=Ctrl],
-kb-keyboard.alt-active kb-modifier-key[char=Alt],
-kb-keyboard.caps-locked kb-shift-key.dark {
-  -webkit-box-shadow: inset 0 0 3px 2px #aaaaaa;
-  background-color: #cccccc;
-}
-
-/**
-* Controls whether the shift key should be highlighted or not.
-*/
-kb-keyboard[keyset="upper"] kb-shift-key.dark /deep/
-    .shift-light {
-    background-color: #4285f4;
-}
-
-.space,
-.dark {
-  font-size: 70%;
-}
-
-.dark:not(.active),
-:not(kb-altkey-set) > :not(.dark).active {
-  background-color: #dddddd;
-}
-
-.space {
-  color: #bbbbbb;
-}