Replace license headers with shorter SPDX header

This means 5 instead of 16 lines, which means less scrolling and less
bloat.

We have started doing these replacements here and there a while ago, but
it seems more efficient to just this once for all files.

Release-Notes: skip
Change-Id: I700f7fbfd51ff3876405c1d240f5b3f9bf2c4e1f

polygerrit-ui/app/elements/admin/gr-admin-group-list/gr-admin-group-list.ts

diff --git a/polygerrit-ui/app/elements/admin/gr-admin-group-list/gr-admin-group-list.ts b/polygerrit-ui/app/elements/admin/gr-admin-group-list/gr-admin-group-list.ts
index 9330f08..e67b838 100644
--- a/polygerrit-ui/app/elements/admin/gr-admin-group-list/gr-admin-group-list.ts
+++ b/polygerrit-ui/app/elements/admin/gr-admin-group-list/gr-admin-group-list.ts
@@ -1,18 +1,7 @@
 /**
  * @license
- * Copyright (C) 2017 The Android Open Source Project
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
+ * Copyright 2017 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
  */
 
 import '../../shared/gr-dialog/gr-dialog';