doc: drop claims of Relay support

This was never fully fleshed out and its probably too complex to do.

src/components/HomepageFeatures/index.tsx

@@ -37,7 +37,7 @@ const FeatureList: FeatureItem[] = [
         <code>TypedDocumentNode</code> which you can use with any client, such as{" "}
         <a href="https://www.apollographql.com/docs/react/">Apollo</a>,{" "}
         <a href="https://formidable.com/open-source/urql/docs/api/urql/">urql</a> or{" "}
-        <a href="https://relay.dev/">Relay</a>
+        <a href="https://github.com/jasonkuhrt/graphql-request">graphql-request</a>
       </>
     ),
   },