No-Vary-Search: further note dependency on a/x-w-fu

Closes #3073.

Author: domenic

draft-ietf-httpbis-no-vary-search.md

@@ -131,7 +131,7 @@ And if the resource instead wants to take an allowlist-based approach, where onl
 No-Vary-Search: params, except=("productId")
 ~~~~
 
-{{header-definition}} defines the header, using the {{STRUCTURED-FIELDS}} framework. {{data-model}} and {{parsing}} illustrate the data model for how the header can be represented in specifications, and the process for parsing the raw output from the structured field parser into that data model. {{comparing}} gives the key algorithm for comparing if two URLs are equivalent under the influence of the header; notably, it leans on the decomposition of the query component into keys and values given by the [application/x-www-form-urlencoded](https://url.spec.whatwg.org/#concept-urlencoded) format specified in {{WHATWG-URL}}. Finally, {{caching}} explains how to modify {{HTTP-CACHING}} to take into account this new equivalence.
+{{header-definition}} defines the header, using the {{STRUCTURED-FIELDS}} framework. {{data-model}} and {{parsing}} illustrate the data model for how the header can be represented in specifications, and the process for parsing the raw output from the structured field parser into that data model. {{comparing}} gives the key algorithm for comparing if two URLs are equivalent under the influence of the header; notably, it leans on the decomposition of the query component into keys and values given by the [application/x-www-form-urlencoded](https://url.spec.whatwg.org/#concept-urlencoded) format specified in {{WHATWG-URL}}. (As such, this header is not useful for URLs whose query component does not follow that format.) Finally, {{caching}} explains how to modify {{HTTP-CACHING}} to take into account this new equivalence.
 
 # Conventions and Definitions