configure.ac: Remove deprecated AC_PROG_LIBTOOL

AC_PROG_LIBTOOL is deprecated version of LT_INIT. Because LT_INIT is
called we can remove it.

Signed-off-by: Ruben Kerkhof <ruben@rubenkerkhof.com>
Reviewed-by: Jan Friesse <jfriesse@redhat.com>

configure.ac

@@ -86,7 +86,6 @@ AC_PROG_INSTALL
 AC_PROG_LN_S
 AC_PROG_MAKE_SET
 AC_PROG_SED
-AC_PROG_LIBTOOL
 
 AC_CHECK_PROGS([GROFF], [groff])
 AC_CHECK_PROGS([PKGCONFIG], [pkg-config])