sysutils/backuppc4: fix smb configuration backup format

See also: https://github.com/backuppc/backuppc/issues/466
See also: https://github.com/backuppc/backuppc/issues/472
Reported by: OlivierW <olivierw1+bugzilla-freebsd@hotmail.com>
PR: 275017
MFH: 2023Q4