faq: update link format (#1178)
faq: update link format (#1178)

* faq: update link format

* Update faq/tidb.md

Co-Authored-By: Calvin Weng <03310b1688af3ac6d84b03af03b0c4d581e884d9@pingcap.com>

pingcap/docs,pingcap/docs,pingcap/docs