TiKV config: update the description of `reserve-space` (#6760)
TiKV config: update the description of `reserve-space` (#6760)

* TiKV config: update the description of `reserve-space`

* Apply suggestions from code review

* Apply suggestions from code review

Co-authored-by: TomShawn <3d0966147538bc5ab020e8dffa2c0b746f9728a6@users.noreply.github.com>

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