[DOC]best_practice describe sendAsyncFailed error

[coder-zzzz]

the https://github.com/apache/rocketmq/blob/master/docs/cn/best_practice.md said
1.2 消息发送失败处理方式
Producer的send方法本身支持内部重试，重试逻辑如下：

至多重试2次（同步发送为2次，异步发送为0次）。

but https://github.com/apache/rocketmq/blob/734834cb560a341dd03f1c738974bc5656e04c87/docs/cn/client/java/API_Reference_DefaultMQProducer.md with retryTimesWhenSendFailed (default 2)

and the code also show it will resend message when send failed by async mode

[duhenglucky]

@coder-zzzz Would you like to pull a request to fix this doc?

[coder-zzzz]

@coder-zzzz Would you like to pull a request to fix this doc?

ok