net-mgmt/librenms: Update to 24.2.0

re: https://github.com/librenms/librenms/releases/tag/24.2.0

This release works with php82 and php83 for me. The previous release
worked on php82, but not php83.

Adjust the pkg-message for so lnms migrate and ./validate.php work
instead of saying you can't run this as root.