Update CONTRIBUTING.md (#4694)
Update CONTRIBUTING.md (#4694)

Signed-off-by: xi <3ae5790a8115be4c26e52deda1e504c94cf29154@whatsoo.org>
c4pt0r/tikv,BusyJay/tikv,BusyJay/tikv,pingcap/tikv,BusyJay/tikv,BusyJay/tikv,pingcap/tikv