fix: typo in docs/sanctuary.md

Fix in docs (field key in readme was wrong):

[error    ] Error validating configuration error_message=1 validation error for Settings
secrets.some-name.from.op-cli-document.document-id
  Field required [type=missing, input_value={'item-id': 'aaaaabbbbccccddddd'}, input_type=dict]
    For further information visit https://errors.pydantic.dev/2.4/v/missing