syslogng: 3.14.1 -> 3.15.1 (#40062)

Semi-automatic update generated by https://github.com/ryantm/nixpkgs-update tools.

This update was made based on information from https://repology.org/metapackage/syslog-ng/versions.

These checks were done:

- built on NixOS
- ran ‘/nix/store/dwmr0h5zbh22ijcwcsg74m301hg8hab9-syslog-ng-3.15.1/bin/loggen -h’ got 0 exit code
- ran ‘/nix/store/dwmr0h5zbh22ijcwcsg74m301hg8hab9-syslog-ng-3.15.1/bin/loggen --help’ got 0 exit code
- ran ‘/nix/store/dwmr0h5zbh22ijcwcsg74m301hg8hab9-syslog-ng-3.15.1/bin/loggen -V’ and found version 3.15.1
- ran ‘/nix/store/dwmr0h5zbh22ijcwcsg74m301hg8hab9-syslog-ng-3.15.1/bin/loggen --version’ and found version 3.15.1
- ran ‘/nix/store/dwmr0h5zbh22ijcwcsg74m301hg8hab9-syslog-ng-3.15.1/bin/syslog-ng -h’ got 0 exit code
- ran ‘/nix/store/dwmr0h5zbh22ijcwcsg74m301hg8hab9-syslog-ng-3.15.1/bin/syslog-ng --help’ got 0 exit code
- ran ‘/nix/store/dwmr0h5zbh22ijcwcsg74m301hg8hab9-syslog-ng-3.15.1/bin/syslog-ng-ctl --help’ got 0 exit code
- ran ‘/nix/store/dwmr0h5zbh22ijcwcsg74m301hg8hab9-syslog-ng-3.15.1/bin/syslog-ng-debun -h’ got 0 exit code
- ran ‘/nix/store/dwmr0h5zbh22ijcwcsg74m301hg8hab9-syslog-ng-3.15.1/bin/syslog-ng-debun help’ got 0 exit code
- found 3.15.1 with grep in /nix/store/dwmr0h5zbh22ijcwcsg74m301hg8hab9-syslog-ng-3.15.1
- directory tree listing: https://gist.github.com/e99978b52b48e592a7c12121b246128c