Fix documentation

Author: orianar

doc/manuals/admin/database_model.md

@@ -284,7 +284,8 @@ Fields:
     is updated each time a notification is sent, to avoid violating throttling.
 -   **throttling**: minimum interval between notifications. 0 or -1 means no throttling.
 -   **reference**: the URL for notifications, either HTTP, MQTT or KAFKA
--   **topic**: MQTT topic (MQTT or KAFKA notifications)
+-   **topic**: MQTT topic (MQTT notifications)
+-   **kafkaTopic**: MQTT topic (KAFKA notifications)
 -   **qos**: MQTT QoS value (only in MQTT notifications)
 -   **retain**: MQTT retain value (only in MQTT notifications)
 -   **entities**: an array of entities (mandatory). The JSON for each