Add jemalloc install instruction for mac (#9879)

### What problem does this PR solve?

Add jemalloc install instruction for mac

### Type of change

- [x] Documentation Update

README_zh.md

@@ -342,6 +342,8 @@ docker build --platform linux/amd64 --build-arg NEED_MIRROR=1 -f Dockerfile -t i
    sudo apt-get install libjemalloc-dev
    # centos
    sudo yum install jemalloc
+   # mac
+   sudo brew install jemalloc
    ```
 
 6. 启动后端服务：