update the usage of tikv-ctl modify-tikv-config (#4132)
update the usage of tikv-ctl modify-tikv-config (#4132)

* update tikv-ctl

Signed-off-by: linning <aaf9d94d942451c9c795db41504f2d244ef7f646@gmail.com>

* Apply suggestions from code review

* Apply suggestions from code review

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