package/samba4: bump version to 4.20.6
Release notes: https://www.samba.org/samba/history/samba-4.20.6.html
Signed-off-by: Bernd Kuhls <bernd@kuhls.net>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
(cherry picked from commit f2355c6702d91eb1d5c428d2c8d204922e101ee9)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>