Updated spatie backup notification config class names

[snipe]

Looks like Spatie changed some class names that we missed in the config. This should correct those method names.

[what-the-diff]

PR Summary

• Updates to Notification Classes
  We have updated the references in our backup configuration file with new class definitions for notification handling. This change aligns each status event (backup failure, unhealthy backup discovery, cleanup failure, successful backup, healthy backup discovery, and successful cleanup) to its corresponding notification class. These updates refine how the system communicates backup states, resulting in clearer, more consistent notifications.