Merge pull request #700 from douglarek/patch-1

[ch20-02-multithreaded.md] typo fix

src/ch20-02-multithreaded.md

@@ -91,7 +91,7 @@
 
 接着编辑 *main.rs* 文件通过在 *src/main.rs* 的开头增加如下代码将 `ThreadPool` 从库 crate 引入作用域：
 
-<span class="filename">文件名：src/bin/main.rs</span>
+<span class="filename">文件名：src/main.rs</span>
 
 ```rust,ignore
 {{#rustdoc_include ../listings/ch20-web-server/no-listing-01-define-threadpool-struct/src/main.rs:here}}