Meta: reference new Structured Field Values RFC

Fetch appears aligned with the changes described in https://httpwg.org/specs/rfc9651.html#changes. Sec-Purpose is the sole structured header Fetch defines and it does not use ABNF for its definition.

fetch.bs

@@ -15,7 +15,7 @@ Translate IDs: typedefdef-bodyinit bodyinit,dictdef-requestinit requestinit,type
 urlPrefix:https://httpwg.org/specs/rfc5861.html#;type:dfn;spec:stale-while-revalidate
     url:n-the-stale-while-revalidate-cache-control-extension;text:stale-while-revalidate lifetime
 
-urlPrefix:https://httpwg.org/specs/rfc8941.html#;type:dfn;spec:rfc8941
+urlPrefix:https://httpwg.org/specs/rfc9651.html#;type:dfn;spec:rfc9651
     url:rfc.section.2;text:structured field value
     url:text-serialize;text:serializing structured fields
     url:text-parse;text:parsing structured fields
@@ -633,7 +633,7 @@ serialize in interesting and efficient ways. For the moment, Fetch only supports
 <a>header values</a> as <a for=/>byte sequences</a>, which means that these objects can be set in
 <a for=/>header lists</a> only via serialization, and they can be obtained from
 <a for=/>header lists</a> only by parsing. In the future the fact that they are objects might be
-preserved end-to-end. [[!RFC8941]]
+preserved end-to-end. [[!RFC9651]]
 </div>
 
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