Update LICENSE
Update LICENSE

修改开源协议类型为GPLv3，维持更好的开源环境。
apache/skywalking,zhangkewei/sky-walking,ascrutae/sky-walking,apache/skywalking,apache/skywalking,ascrutae/sky-walking,apache/skywalking,OpenSkywalking/skywalking,OpenSkywalking/skywalking,ascrutae/sky-walking,zhangkewei/sky-walking,hanahmily/sky-walking,apache/skywalking,ascrutae/sky-walking,apache/skywalking,hanahmily/sky-walking,apache/skywalking