Graylog check this URL to get latest available version:
https://versioncheck.graylog.com/check
You have 3 options:
- Add this parameter to /etc/graylog/server/server.conf:
versionchecks = false
- Or disable this url in your proxy, firewall, /etc/hosts file
- Or create script, that will delete notification using API:
/api/system/notifications/outdated_version