package/samba4: security bump to version 4.15.12

Fixes the following security issue:

- CVE-2022-42898: Samba buffer overflow vulnerabilities on 32-bit systems
  https://www.samba.org/samba/security/CVE-2022-42898.html



Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>