fixed license version

src/com/owncloud/android/ui/adapter/FilterableListAdapter.java

@@ -5,7 +5,7 @@
  *   Copyright (C) 2016 Nextcloud.
  *
  *   This program is free software: you can redistribute it and/or modify
- *   it under the terms of the GNU General Public License version 2,
+ *   it under the terms of the GNU General Public License version 3,
  *   as published by the Free Software Foundation.
  *
  *   This program is distributed in the hope that it will be useful,