feat: tweak `picodata expel` arguments

Summary

• feat: tweak picodata expel arguments

$ picodata help expel
picodata-expel 
Expel node from cluster

USAGE:
    picodata expel [OPTIONS] <INSTANCE_ID>

ARGS:
    <INSTANCE_ID>    Name of the instance to expel

OPTIONS:
        --cluster-id <NAME>
            Name of the cluster from instance should be expelled [env: PICODATA_CLUSTER_ID=]
            [default: demo]

    -h, --help
            Print help information

        --password-file <PASSWORD_FILE>
            Path to a plain-text file with the `admin` password. If this option isn't provided, the
            password is prompted from the terminal [env: PICODATA_PASSWORD_FILE=]

        --peer <[HOST][:PORT]>
            Address of any picodata instance of the given cluster [env: PICODATA_PEER=] [default:
            localhost:3301]

Docs screenshot

• https://docs.binary.picodata.io/picodata/expel/reference/cli/#expel

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• Close #561 (closed)
• See also docs!346 (merged)
• Target branch: master
• Changes should be cherry-picked to 24.2: yes
• Docs follow-up: not necessary