package/samba4: bump version to 4.21.7
Release notes:
https://www.samba.org/samba/history/samba-4.21.7.html
Signed-off-by: Bernd Kuhls <bernd@kuhls.net>
Signed-off-by: Julien Olivain <ju.o@free.fr>
(cherry picked from commit 282e7add8806bb629c18cc84155542d89746710a)
[Titouan: Bump to 4.21.7 on buildroot 2025.02]
Signed-off-by: Titouan Christophe <titouan.christophe@mind.be>