maint: regenerate bootstrap

Commit 3ad13c92 blindly touched all files to have a 3-line
hint for getting LGPL, but bootstrap is synced from gnulib where
it has a 2-line hint.

* bootstrap: Resync from gnulib.

bootstrap

@@ -17,8 +17,7 @@ scriptversion=2012-07-19.14; # UTC
 # 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, see
-# <http://www.gnu.org/licenses/>.
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 # Originally written by Paul Eggert.  The canonical version of this
 # script is maintained as build-aux/bootstrap in gnulib, however, to