syslog-ng: bump version header in conf file to 3.10

Remove a runtime warning message about configuration file being too old.

Do the same as commit 3dad25466d "syslog-ng: Bump version header in conf
file to 3.9". Package version of syslog-ng is 3.10.1, so bump version
number in syslog-ng.conf to 3.10.

Also add a comment to avoid the same warning message reappears when the
package is bumped.

Signed-off-by: Ricardo Martincoski <ricardo.martincoski@datacom.ind.br>
Cc: Chris Packham <judge.packham@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

package/syslog-ng/syslog-ng.conf

@@ -1,4 +1,4 @@
-@version: 3.9
+@version: 3.10
 
 source s_sys {
 	file("/proc/kmsg" program_override("kernel"));

package/syslog-ng/syslog-ng.mk

@@ -4,6 +4,8 @@
 #
 ################################################################################
 
+# When updating the version, please check at runtime if the version in
+# syslog-ng.conf header needs to be updated
 SYSLOG_NG_VERSION = 3.10.1
 SYSLOG_NG_SITE = https://github.com/balabit/syslog-ng/releases/download/syslog-ng-$(SYSLOG_NG_VERSION)
 SYSLOG_NG_LICENSE = LGPL-2.1+ (syslog-ng core), GPL-2.0+ (modules)