Update End of Life announcement.

[weiting-chen]

What changes were proposed in this pull request?

End of Life announcement for Gazelle.

How was this patch tested?

n/a, only README change

[github-actions[bot]]

Thanks for opening a pull request!

Could you open an issue for this pull request on Github Issues?

https://github.com/oap-project/native-sql-engine/issues

Then could you also rename commit message and pull request title in the following format?

[NSE-${ISSUES_ID}] ${detailed message}

See also:

• Other pull requests