package/syslog-ng: update version in config file

syslog-ng warns when using a configuration from an older version. Update
the version in the example config.

Fixes: 9695f3e069 ("package/syslog-ng: bump version to 3.22.1")
Signed-off-by: Chris Packham <judge.packham@gmail.com>
Tested-by: Carlos Santos <unixmania@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

package/syslog-ng/syslog-ng.conf

@@ -1,4 +1,4 @@
-@version: 3.19
+@version: 3.22
 
 source s_sys {
 	file("/proc/kmsg" program_override("kernel"));