Incorrect example in readme

[maoshunyu]

https://github.com/aliyun/aicb?tab=readme-ov-file#generating-the-workload-description-files-for-moe

Looks like it should be --ep 16 instead of --ep_num 16

[zhouheyang-alibaba]

Recently, there have been some updates in this area. I apologize for not thoroughly reviewing the contents of the README. I will test it and update the commands here.