Editorial: change alt text of outline image (whatwg#1671)

Image introduced in bd6758b

Also fix a nearby typo.

source

@@ -15932,7 +15932,7 @@ Space is not the only void</pre>
       </li>
       <li>
        <p><strong>Section implied for second <code>h2</code> element.</strong></p>
-       <p>Associated with heading <code data-x="">&lt;h2>First section>&lt;/h2></code>.</p>
+       <p>Associated with heading <code data-x="">&lt;h2>First section&lt;/h2></code>.</p>
        <p>Also associated with the paragraph <code data-x="">&lt;p>Some intro to the first
        section.&lt;/p></code> (though it likely would not be shown in a rendered view of the
        outline).</p>
@@ -15944,8 +15944,9 @@ Space is not the only void</pre>
 
    <p>The following image shows what a rendered view of the outline might look like.</p>
 
-   <p><img src="/images/outline.svg" width="465" height="120"
-           alt="Outline showing rendering of a multi-level heading and other headings."></p>
+   <p><img src="/images/outline.svg" width="465" height="120" alt="Top-level section with the
+   multi-level heading &quot;HTML: Living Standard — Last Updated 12 August 2016&quot; and two
+   subsections; &quot;Table of contents&quot; and &quot;First section&quot;."></p>
   </div>
 
   <div w-nodev>