message: Fix EventIndex handling events twice
  It awaits the decryption in onRoomTimeline as well as subscribing to EVent.decrypted
diff: @@ -67,7 +67,6 @@ export default class EventIndex extends EventEmitter {
  client.on('sync', this.onSync);
  client.on('Room.timeline', this.onRoomTimeline);
  - client.on('Event.decrypted', this.onEventDecrypted);
  client.on('Room.timelineReset', this.onTimelineReset);
  client.on('Room.redaction', this.onRedaction);
  client.on('RoomState.events', this.onRoomStateEvent);
  @@ -82,7 +81,6 @@ export default class EventIndex extends EventEmitter {
  client.removeListener('sync', this.onSync);
  client.removeListener('Room.timeline', this.onRoomTimeline);
  - client.removeListener('Event.decrypted', this.onEventDecrypted);
  client.removeListener('Room.timelineReset', this.onTimelineReset);
  client.removeListener('Room.redaction', this.onRedaction);
  client.removeListener('RoomState.events', this.onRoomStateEvent);
  @@ -221,18 +219,6 @@ export default class EventIndex extends EventEmitter {
  }
  };
  - /*
  - * The Event.decrypted listener.
  - *
  - * Checks if the event was marked for addition in the Room.timeline
  - * listener, if so queues it up to be added to the index.
  - */
  - private onEventDecrypted = async (ev: MatrixEvent, err: Error) => {
  - // If the event isn't in our live event set, ignore it.
  - if (err) return;
  - await this.addLiveEventToIndex(ev);
  - };
  -
  /*
  * The Room.redaction listener.
  *
  