Fix broken reference to RFC7230 (#406)

RFC7230 is replaced with RFC9110; update the reference to list ABNF syntax accordingly

Closes: #404

index.html

@@ -1001,7 +1001,7 @@ <h4>
             allowed to see values of attributes that would have been zero due
             to the cross-origin restrictions. The header's value is represented
             by the following ABNF [[RFC5234]] (using <a data-cite=
-            "RFC7230#section-7">List Extension</a>, [[RFC7230]]):
+            "RFC9110#rfc.section.5.6.1">List Extension</a>, [[RFC9110]]):
           </p><code class="abnf">Timing-Allow-Origin = 1#( <a data-cite=
           "FETCH#origin-header">origin-or-null</a> / <a data-cite=
           "FETCH#http-new-header-syntax">wildcard</a> )</code>