Fix incorrect file path (404 Not Found)

Issue Description
A 404 error occurred when accessing the repository link pointing to README_zh.md. Upon inspection, the actual file path is README-zh.md, indicating an incorrect path reference in the original link.

Fix Details
Corrected the broken link from README_zh.md to the correct path README-zh.md.

Verification Method
After modification, the target file opens normally in the browser.

Hope this fix helps users access the Chinese documentation properly—thanks for the review!

README-zh.md

@@ -30,7 +30,7 @@
       <a href="https://github.com/HKUDS/LightRAG/issues/285"><img src="https://img.shields.io/badge/💬微信群-交流-07c160?style=for-the-badge&logo=wechat&logoColor=white&labelColor=1a1a2e"></a>
     </p>
     <p>
-      <a href="README_zh.md"><img src="https://img.shields.io/badge/🇨🇳中文版-1a1a2e?style=for-the-badge"></a>
+      <a href="README-zh.md"><img src="https://img.shields.io/badge/🇨🇳中文版-1a1a2e?style=for-the-badge"></a>
       <a href="README.md"><img src="https://img.shields.io/badge/🇺🇸English-1a1a2e?style=for-the-badge"></a>
     </p>
   </div>