Fix small audio events details (#6978)

* Fix missed audio details

* Add mqtt docs

* Delete instead of setting to None

frigate/comms/mqtt.py

@@ -149,6 +149,7 @@ class MqttClient(Communicator):  # type: ignore[misc]
             "recordings",
             "snapshots",
             "detect",
+            "audio",
             "motion",
             "improve_contrast",
             "motion_threshold",

frigate/events/audio.py

@@ -206,7 +206,7 @@ class AudioEventMaintainer(threading.Thread):
                 now - detection.get("last_detection", now)
                 > self.config.audio.max_not_heard
             ):
-                self.detections[detection["label"]] = None
+                del self.detections[detection["label"]]
                 requests.put(
                     f"{FRIGATE_LOCALHOST}/api/events/{detection['id']}/end",
                     json={