🩹(frontend) clean up notifications when participant quits

When a participant leaves a videoconference, remove all notifications they
authored. It's generally unnecessary to keep notifications about actions from
users who are no longer present, with few exceptions.

As we currently support only two notification types (Joined and Raised Hand),
it's appropriate to close all of them when the author leaves the room.

src/frontend/src/features/notifications/MainNotificationToast.tsx

@@ -34,19 +34,19 @@ export const MainNotificationToast = () => {
   }, [room, triggerNotificationSound])
 
   useEffect(() => {
-    const removeJoinNotification = (participant: Participant) => {
-      const existingToast = toastQueue.visibleToasts.find(
-        (toast) =>
-          toast.content.participant === participant &&
-          toast.content.type === NotificationType.Joined
-      )
-      if (existingToast) {
-        toastQueue.close(existingToast.key)
-      }
+    const removeParticipantNotifications = (participant: Participant) => {
+      toastQueue.visibleToasts.forEach((toast) => {
+        if (toast.content.participant === participant) {
+          toastQueue.close(toast.key)
+        }
+      })
     }
-    room.on(RoomEvent.ParticipantDisconnected, removeJoinNotification)
+    room.on(RoomEvent.ParticipantDisconnected, removeParticipantNotifications)
     return () => {
-      room.off(RoomEvent.ParticipantConnected, removeJoinNotification)
+      room.off(
+        RoomEvent.ParticipantDisconnected,
+        removeParticipantNotifications
+      )
     }
   }, [room])