fix broken links in readme (#505)

readme.md

@@ -207,7 +207,7 @@ go get -u github.com/tal-tech/go-zero
 ## 8. Documents (adding)
 
 * [Rapid development of microservice systems](https://github.com/tal-tech/zero-doc/blob/main/doc/shorturl-en.md)
-* [Rapid development of microservice systems - multiple RPCs](https://github.com/tal-tech/zero-doc/blob/main/doc/bookstore-en.md)
+* [Rapid development of microservice systems - multiple RPCs](https://github.com/tal-tech/zero-doc/blob/main/docs/zero/bookstore-en.md)
 * [Examples](https://github.com/zeromicro/zero-examples)
 
 ## 9. Chat group