delete assignment of readonly property (message.covId/clientId/msgId/status)
delete assignment of readonly property (message.covId/clientId/msgId/status)

lzwjava/leanchat-ios,leancloud/leanchat-ios,lzwjava/leanchat-ios,leancloud/leanchat-ios,lzwjava/leanchat-ios,leancloud/leanchat-ios