Remove one Chinese markdown tutorial with another one (#3925)

free-programming-books-zh.md

@@ -585,7 +585,7 @@
 
 ### Markdown
 
-* [Markdown 简明教程](http://www.jianshu.com/p/7bd23251da0a)
+* [Markdown 語法說明](https://markdown.tw)
 * [献给写作者的 Markdown 新手指南](http://www.jianshu.com/p/q81RER)