Update software version and release date

Author: laf

publiccode.yml

@@ -4,8 +4,8 @@ applicationSuite: Others
 url: https://github.com/librenms/librenms
 landingURL: https://www.librenms.org
 isBasedOn: https://www.observium.org
-softwareVersion: 26.4.0
-releaseDate: 2026-03-16
+softwareVersion: 26.5.1
+releaseDate: 2026-05-20
 logo: https://github.com/librenms/librenms.github.io/blob/master/images/LibreNMS-Logo-Black.svg
 platforms:
   - linux