*: make GNU licensing statement forms more regular

This change retains "or later" state! No licensing _changes_ here,
only form is adjusted (article, space between "GPL" and "v2" and so on).

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/libbb/update_passwd.c b/libbb/update_passwd.c
index f5ce1f9..e050dfc 100644
--- a/libbb/update_passwd.c
+++ b/libbb/update_passwd.c
@@ -11,7 +11,7 @@
  * Modified to be able to add or delete users, groups and users to/from groups
  * by Tito Ragusa <farmatito@tiscali.it>
  *
- * Licensed under GPLv2, see file LICENSE in this tarball for details.
+ * Licensed under GPLv2, see file LICENSE in this source tree.
  */
 #include "libbb.h"