docs: fix English README link

Fix broken English README link in README_CN.md: badge pointed to README_EN.md but the English README is README.md (404). Closes #6365

Author: zhonggang666

README_CN.md

@@ -4,7 +4,7 @@
     <a href="https://trendshift.io/repositories/9113" target="_blank"><img src="https://trendshift.io/api/badge/repositories/9113" alt="1Panel-dev%2FMaxKB | Trendshift" style="width: 250px; height: auto;" /></a>
 </p>
 <p align="center">
-  <a href="README_EN.md"><img src="https://img.shields.io/badge/English_README-blue" alt="English README"></a>
+  <a href="README.md"><img src="https://img.shields.io/badge/English_README-blue" alt="English README"></a>
   <a href="https://www.gnu.org/licenses/gpl-3.0.html#license-text"><img src="https://img.shields.io/github/license/1Panel-dev/maxkb?color=%231890FF" alt="License: GPL v3"></a>
   <a href="https://github.com/1Panel-dev/maxkb/releases/latest"><img src="https://img.shields.io/github/v/release/1Panel-dev/maxkb" alt="Latest release"></a>
   <a href="https://github.com/1Panel-dev/maxkb"><img src="https://img.shields.io/github/stars/1Panel-dev/maxkb?style=flat-square" alt="Stars"></a>