add documentation for the PresenceExpired metric
| ---------------------------------------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------- | ---- |
| `ActiveLocks` | Total number of active locks. Emitted periodically. | number |
| `ActivePresences` | Total number of active presences. Emitted periodically. | number |
-| `LocksExpired` | Cumulative number of locks/presences that have expired. Emitted when a lock or presence is expired. | number |
+| `LocksExpired` | Cumulative number of locks that have expired. Emitted when a lock is expired. | number |
+| `PresenceExpired` | Cumulative number of presences that have expired. Emitted when a presence is expired. | number |
## Rep
