Deleted lines should not be considered to return a completion record from an AO

[ptomato]

Test case:

<emu-clause id="sec-foobar" type="abstract operation">
  <h1>
    FooBar (
      _v_: an ECMAScript language value,
    ): <ins>an integer</ins><del>either a normal completion containing an integer, or a throw completion</del>
  </h1>
  <dl class="header">
    <dt>description</dt>
    <dd></dd>
  </dl>
  <emu-alg>
    1. <del>Throw a *RangeError* exception.</del>
    1. Return 42.
  </emu-alg>
</emu-clause>

This produces:

(file):5:23: unknown extra text in header
(file):12:13: this would return a Completion Record, but the containing AO is declared not to return a Completion Record

Looks like there is something that needs to be handled differently about the structured header return type, as well.