syslog-ng: Bump version header in conf file to 3.9

Package version of syslog-ng is 3.9.1.
Bumping version number in syslog-ng.conf to 3.9

Fixing warning message about configuration file being too old.

Signed-off-by: Pawel Sikora <sikor6@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/syslog-ng/syslog-ng.conf

@@ -1,4 +1,4 @@
-@version: 3.7
+@version: 3.9
 
 source s_sys {
 	file("/proc/kmsg" program_override("kernel"));