disabled_transport_categories setting on an audit logging config may be unnecessary after transport client removal

[cwperks]

Since OpenSearch 2.0, support for the transport client has been removed. The transport client was removed from the security plugin in this PR: #1701

My understanding of disabled_transport_categories is that it is used to enable an audit logging to log events from originating from the transport client.

Below is an example of a audit logging config of the security plugin's audit.yml file from the demo configuration:

config:
  # enable/disable audit logging
  enabled: true

  audit:
    # Enable/disable REST API auditing
    enable_rest: true

    # Categories to exclude from REST API auditing
    disabled_rest_categories:
      - AUTHENTICATED
      - GRANTED_PRIVILEGES

    # Enable/disable Transport API auditing
    enable_transport: true

    # Categories to exclude from Transport API auditing
    disabled_transport_categories:
      - AUTHENTICATED
      - GRANTED_PRIVILEGES

The disabled_transport_categories setting may not be needed here after the TransportClient's removal.

First: Determine if it is safe to remove values from settings.
Second: If safe to remove, remove. If not, update documentation.

[davidlago]

[Triaging] Need more clear determination of whether TransportClient related codepaths can be removed, and also clearer exit criteria for the issue.

[stephen-crawford]

[Triage] This looks like the exit criteria and additional info has been added.