Add required phrase tag to rule

Reference: https://github.com/plougher/squashfs-tools/blob/master/squashfs-tools/xz_wrapper_extended.c#L5
Signed-off-by: Philippe Ombredanne <pombredanne@aboutcode.org>

Author: pombredanne

src/licensedcode/data/rules/gpl-2.0-plus_1156.RULE

@@ -4,9 +4,9 @@ is_license_notice: yes
 ---
 
  * This program is free software; you can redistribute it and/or
- * modify it under the terms of the GNU General Public License
+ * modify it under the terms of the {{GNU General Public License
  * as published by the Free Software Foundation; either version 2,
- * or (at your option) any later version.
+ * 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