Fix raised hand handler not detached when peer is destroyed

This fixes a memory leak, as the reference to the Peer object was
retained forever by the webrtc object.

Signed-off-by: Daniel Calviño Sánchez <danxuliu@gmail.com>

src/utils/webrtc/models/CallParticipantModel.js

@@ -97,6 +97,7 @@ CallParticipantModel.prototype = {
 		this._webRtc.off('mute', this._handleMuteBound)
 		this._webRtc.off('unmute', this._handleUnmuteBound)
 		this._webRtc.off('channelMessage', this._handleChannelMessageBound)
+		this._webRtc.off('raisedHand', this._handleRaisedHandBound)
 	},
 
 	get: function(key) {