faq: update descriptions about deploying TiDB on cloud (#4005)
faq: update descriptions about deploying TiDB on cloud (#4005)

* Modify wording in FAQ

* Update tidb-faq.md

* Apply suggestions from code review

Co-authored-by: Lilian Lee <c684465c17314189c18707959627e2ec4fdec2d0@pingcap.com>
pingcap/docs-cn,pingcap/docs-cn