docs: fix broken link

Author: asnowwolf

readme_zh.md

@@ -23,7 +23,7 @@
   [![Sponsors on Open Collective](https://opencollective.com/nest/sponsors/badge.svg)](https://opencollective.com/nest#sponsor)-->
 
 
-### [English](readme.md)
+### [English](Readme.md)
 
 ## 介绍