Editorial: parsing application/x-www-form-urlencoded never fails

Fixes #1798.

Author: annevk

fetch.bs

@@ -7418,8 +7418,6 @@ running <a for=Body>consume body</a> with <a>this</a> and the following steps gi
      <li><p>Let <var>entries</var> be the result of  <a lt="urlencoded parser">parsing</a>
      <var>bytes</var>.
 
-     <li><p>If <var>entries</var> is failure, then <a>throw</a> a {{TypeError}}.
-
      <li><p>Return a new {{FormData}} object whose <a for=FormData>entry list</a> is
      <var>entries</var>.
     </ol>