[docs] Fix broken releases link
<p align="center">Addax is an open source universal ETL tool</p>
<p align="center"><a href="https://wgzhao.github.io/Addax">Documentation</a> detailed description of how to install and deploy and how to use each collection plugin </p>
<p align="center">
- <a href="https://github.com/wgzhao/addax/release">
+ <a href="https://github.com/wgzhao/Addax/releases">
<img src="https://img.shields.io/github/release/wgzhao/addax.svg" alt="release version"/>
</a>
<a href="https://github.com/wgzhao/Addax/workflows/Maven%20Package/badge.svg">
