If the Analytics Data Insertion API doesn't require any authentication, you don't need `require-adobe-auth`. However, I understand that you still want "some protection" for your action.
What you could do is adding `require-whisk-auth` to the manifest, its value is a secret hash. Then from the calling system you make request to your action with this header `X-Require-Whisk-Auth: secret_hash`. Other requests without this header would be rejected.