change license declaration

httpclient/httpclient_sample.c

@@ -1,23 +1,12 @@
-/*
+/* 
  * File      : httpclient.c
- * COPYRIGHT (C) 2006 - 2018, RT-Thread Development Team
  *
- *  This program is free software; you can redistribute it and/or modify
- *  it under the terms of the GNU General Public License as published by
- *  the Free Software Foundation; either version 2 of the License, or
- *  (at your option) any later version.
- *
- *  This program is distributed in the hope that it will be useful,
- *  but WITHOUT ANY WARRANTY; without even the implied warranty of
- *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- *  GNU General Public License for more details.
- *
- *  You should have received a copy of the GNU General Public License along
- *  with this program; if not, write to the Free Software Foundation, Inc.,
- *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
- *
- * Change Logs:
- * Date           Author       Notes
+ * Copyright (c) 2006-2018, RT-Thread Development Team 
+ * 
+ * SPDX-License-Identifier: Apache-2.0 
+ * 
+ * Change Logs: 
+ * Date             Author      Notes
  * 2018-07-20     flybreak     first version
  */