Use SPDX identifier.

Author: bicknellr

packages/shadydom/src/selector-parser.js

@@ -1,12 +1,7 @@
 /**
  * @license
- * Copyright (c) 2022 The Polymer Project Authors. All rights reserved. This
- * code may only be used under the BSD style license found at
- * http://polymer.github.io/LICENSE.txt The complete set of authors may be found
- * at http://polymer.github.io/AUTHORS.txt The complete set of contributors may
- * be found at http://polymer.github.io/CONTRIBUTORS.txt Code distributed by
- * Google as part of the polymer project is also subject to an additional IP
- * rights grant found at http://polymer.github.io/PATENTS.txt
+ * Copyright (c) 2022 The Polymer Project Authors
+ * SPDX-License-Identifier: BSD-3-Clause
  */
 
 /**