Update Xcode reference from message.mp3 to message.caf.
Update Xcode reference from message.mp3 to message.caf.

vector-im/riot-ios,vector-im/riot-ios,vector-im/riot-ios,vector-im/riot-ios,vector-im/riot-ios,vector-im/vector-ios,vector-im/riot-ios,vector-im/vector-ios,vector-im/vector-ios