Intentional reference to obsoleted rfc assigned to the updating rfc

[jyasskin]

https://pr-preview.s3.amazonaws.com/jyasskin/webpackage/pull/712.html#term-for-section-3.3%E2%91%A1 claims that rfc9162 defines signedcertificatetimestamplist even though the definition in the anchors section cites RFC6962. We're intentionally staying on the old one, and the new one removed the definition of the old one's structures, so I can't just refer to the new RFC.

[tabatkins]

Ah, I suppose the code following spec references when assembling the list from links isn't aware of the explicit biblio stuff. I should be able to tell that a ref comes from an anchors-block, tho, and honor your exact document. Will fix.