Update getCommittee epoch query parameter

[Thoralf-M]

Description of change

Change it from epochIndex to epoch

Type of change

• Breaking change (fix or feature that would cause existing functionality to not work as expected)

How the change has been tested

    let committee_response = client.get_committee(None).await?;
    let committee_response2 = client.get_committee(committee_response.epoch - 1).await?;