Update haproxy-best-practices.md (#7805)
Update haproxy-best-practices.md (#7805)

* Update haproxy-best-practices.md

* Update best-practices/haproxy-best-practices.md

Co-authored-by: Lilian Lee <c684465c17314189c18707959627e2ec4fdec2d0@pingcap.com>

* add maxconn description

* remove brackets

Co-authored-by: Lilian Lee <c684465c17314189c18707959627e2ec4fdec2d0@pingcap.com>
Co-authored-by: TomShawn <3d0966147538bc5ab020e8dffa2c0b746f9728a6@users.noreply.github.com>
pingcap/docs-cn,pingcap/docs-cn