Update Nacos to 2.0.4 in Spring Cloud Alibaba 2021.x branch

[steverao]

我们鼓励使用英文，如果不能直接使用，可以使用翻译软件，您仍旧可以保留中文原文。
We recommend using English. If you are non-native English speaker, you can use the translation software.

Which Component
eg. Nacos,

Is your feature request related to a problem? Please describe.
We are prepared to release a new version of Spring Cloud Alibaba in 2021.x branch, we are plan to update some components.

Describe the solution you'd like
A clear and concise description of what you want to happen.
Update Nacos to 2.0.4 in Spring Cloud Alibaba 2021.x branch, and test the reliability.