configure.ac: run autoupdate to fix autoconf warning

This fixes the following warning:

    $ autoconf
    configure.ac:306: warning: AC_OUTPUT should be used without arguments.
    configure.ac:306: You should run autoupdate.

Environment:

    $ grep '^NAME' /etc/os-release
    NAME="Artix Linux"
    $ pacman -Q autoconf
    autoconf 2.71-1

Though keep `AC_PREREQ` at 2.68 (released on 2010-09-23[1]), as version
2.71 (which autoupdate automatically bumps to) is rather recent
(released on 2021-01-28[2]) and the changes do not appear to require a
version bump, as on `AC_INIT` it only adds some quotes, and the rest of
the changes are consistent with the autoconf 2.68 manual.  From Section
18.4, Obsolete Macros[3]:

> — Macro: AC_OUTPUT ([file]..., [extra-cmds], [init-cmds])
>
>     The use of AC_OUTPUT with arguments is deprecated.  This obsoleted
>     interface is equivalent to:
>
>               AC_CONFIG_FILES(file...)
>               AC_CONFIG_COMMANDS([default],
>                                  extra-cmds, init-cmds)
>               AC_OUTPUT
>
>     See AC_CONFIG_FILES, AC_CONFIG_COMMANDS, and AC_OUTPUT.

Note: The usage of the above format has been present since the inception
of configure.ac, on commit 1379851 ("Baseline firejail 0.9.28").

Misc: This is a continuation of #4293.

[1] https://lists.gnu.org/archive/html/info-gnu/2010-09/msg00013.html
[2] https://lists.gnu.org/archive/html/autoconf/2021-01/msg00126.html
[3] https://www.gnu.org/software/autoconf/manual/autoconf-2.68/html_node/Obsolete-Macros.html#index-AC_005fOUTPUT-2058

configure.ac

@@ -12,7 +12,7 @@
 #
 
 AC_PREREQ([2.68])
-AC_INIT(firejail, 0.9.65, [email protected], , https://firejail.wordpress.com)
+AC_INIT([firejail],[0.9.65],[[email protected]],[],[https://firejail.wordpress.com])
 AC_CONFIG_SRCDIR([src/firejail/main.c])
 
 AC_CONFIG_MACRO_DIR([m4])
@@ -304,11 +304,12 @@ if test "$prefix" = /usr; then
 fi
 
 AC_CONFIG_FILES([mkdeb.sh], [chmod +x mkdeb.sh])
-AC_OUTPUT(Makefile src/common.mk src/lib/Makefile src/fcopy/Makefile src/fnet/Makefile src/firejail/Makefile src/fnetfilter/Makefile \
+AC_CONFIG_FILES([Makefile src/common.mk src/lib/Makefile src/fcopy/Makefile src/fnet/Makefile src/firejail/Makefile src/fnetfilter/Makefile \
 src/firemon/Makefile src/libtrace/Makefile src/libtracelog/Makefile src/firecfg/Makefile src/fbuilder/Makefile src/fsec-print/Makefile \
 src/ftee/Makefile src/fseccomp/Makefile src/fldd/Makefile src/libpostexecseccomp/Makefile src/fsec-optimize/Makefile \
 src/profstats/Makefile src/man/Makefile src/zsh_completion/Makefile src/bash_completion/Makefile test/Makefile \
-src/jailcheck/Makefile)
+src/jailcheck/Makefile])
+AC_OUTPUT
 
 echo
 echo "Configuration options:"