Explain what to do about a echidna.deliverer-change failure

[jyasskin]

https://github.com/w3ctag/security-questionnaire/actions/runs/12679739460/job/35340072483 has a failure that

The list of groups producing this document has changed since the previous version

      {
        name: 'echidna.deliverer-change',
        section: 'metadata',
        rule: 'delivererID'
      }

This is true (TAG + Privacy IG => TAG + Privacy WG + Security IG), but it's not clear what the spec's editors should do about it. The error message should give us some guidance.

[deniak]

@jyasskin we will update the error message.
In the meantime, if there's a change of deliverers for a spec, we will need to publish it manually.
@ylafon can you please prepare the doc and send the request to webreq?