fix: use the new event system on the demo (#10)

* compilable demo

* correctly close room_task

* wip

* fix demo

crates/livekit-core/src/room/room_session.rs

@@ -199,7 +199,7 @@ impl SessionInner {
                                 error!("failed to handle participant event for {:?}: {:?}", participant.sid(), err);
                             }
                         },
-                        _ => panic!("engine_events has been closed unexpectedly")
+                        _ => panic!("participant_events has been closed unexpectedly")
                     };
                 },
                 _ = &mut close_rx => {

crates/livekit-utils/src/observer.rs

@@ -34,6 +34,6 @@ where
 
     pub fn dispatch(&mut self, msg: &T) {
         self.senders
-            .retain(|sender| sender.send(msg.clone()).is_err());
+            .retain(|sender| sender.send(msg.clone()).is_ok());
     }
 }