[doc] fix krypton and master on setup-rw-svc.md

[hustjieke]

Is your feature request related to a problem? Please describe.

e.g.:

# kubectl exec -ti $pod -c xenon xenoncli raft status | jq .leader | cut -d . -f 1 | tail -c +2
demo-krypton-1
# kubectl label pods $leader role=master

Describe the solution you'd like

Describe alternatives you've considered

Additional context