toc: remove docs home from left navigation (pingcap#20722) (pingcap#20724)

Author: ti-chi-bot

TOC.md

@@ -1,7 +1,6 @@
 <!-- markdownlint-disable MD007 -->
 <!-- markdownlint-disable MD041 -->
 
-- [文档中心](https://docs.pingcap.com/zh)
 - 关于 TiDB
   - [TiDB 简介](/overview.md)
   - [TiDB 8.1 Release Notes](/releases/release-8.1.0.md)