fixed: 文末的返回顶部链接问题

Author: Dacheng Gao

README.md

@@ -1962,4 +1962,4 @@ This is also available in other languages:
    * [yangweijie/clean-code-php](https://github.com/yangweijie/clean-code-php)
    * [php-cpm/clean-code-php](https://github.com/php-cpm/clean-code-php)
 
-**[⬆ back to top](#table-of-contents)**
+**[⬆ back to top](#目录)**