Editorial: use "isomorphic decode" for Refresh header steps

Fixes #3924.

source

@@ -2524,6 +2524,7 @@ a.setAttribute('href', 'https://example.com/'); // change the content attribute
      <li><dfn id="lowercase-ascii-letters" data-x-href="https://infra.spec.whatwg.org/#ascii-lower-alpha">ASCII lower alpha</dfn></li>
      <li><dfn id="ascii-letters" data-x-href="https://infra.spec.whatwg.org/#ascii-alpha">ASCII alpha</dfn></li>
      <li><dfn id="alphanumeric-ascii-characters" data-x-href="https://infra.spec.whatwg.org/#ascii-alphanumeric">ASCII alphanumeric</dfn></li>
+     <li><dfn data-x-href="https://infra.spec.whatwg.org/#isomorphic-decode">isomorphic decode</dfn></li>
      <li><dfn data-x="converted to ASCII lowercase" data-x-href="https://infra.spec.whatwg.org/#ascii-lowercase">ASCII lowercase</dfn></li>
      <li><dfn data-x="converted to ASCII uppercase" data-x-href="https://infra.spec.whatwg.org/#ascii-uppercase">ASCII uppercase</dfn></li>
      <li><dfn data-x-href="https://infra.spec.whatwg.org/#ascii-case-insensitive">ASCII case-insensitive</dfn></li>
@@ -82519,8 +82520,8 @@ interface <dfn>Location</dfn> { // but see also <a href="#the-location-interface
        href="https://github.com/whatwg/html/issues/2900">Multiple `<code
        data-x="http-refresh">Refresh</code>` headers</a>.</p></li>
 
-       <li><p>Let <var>value</var> be the value of the header with each byte mapped to a code point
-       of equal value.</p></li>
+       <li><p>Let <var>value</var> be the <span data-x="isomorphic decode">isomorphic decoding</span>
+       of the value of the header.</p></li>
 
        <li><p>Run the <span>shared declarative refresh steps</span> with the <code>Document</code>
        and <var>value</var>.</p></li>