Timelock migration docs weren't updated since conjure-java migration

[jeremyk-91]

We have cluster management docs for upgrading a 1 to 3 node cluster. These use curls from before the conjure java migration, so something like

curl -XGET https://<timelock-host>:<timelock-port>/timelock/api/leader/<client>/timelock/fresh-timestamp

But this is wrong after the conjure java migration. You need something closer to

curl -k -XPOST https://host:port/timelock/api/tl/ts/<client> --data '{"numTimestamps": 1}' -H "Bearer: Auth unused"

Docs should be updated.