Specs rely on expired versions of Structured Headers draft

[clelland]

draft-yasskin-httpbis-origin-signed-exchanges-impl.md appears to be pinned to Structured Headers draft 10, which expired in April. parser.go looks like it references version 9. draft-yasskin-http-origin-signed-responses.md is not pinned to any particular version, and so generates references to the latest draft (13) when built, but references concepts which do not exist in that draft.

Current versions do not use 'Parameterised List' any more, but the general 'List' structure should suffice for signed-exchanges, likely without any effective syntax changes.