README: remove TiDB Monthly (pingcap#1233)

Author: CaitinChen

README.md

@@ -69,5 +69,3 @@ Parser is under the Apache 2.0 license. See the LICENSE file for details.
 
     - [English](https://pingcap.com/blog/)
     - [简体中文](https://pingcap.com/blog-cn/)
-
-- [TiDB Monthly](https://pingcap.com/weekly/)