Fix incorrect dialog assert

Author: keithamus

source

@@ -62906,8 +62906,8 @@ interface <dfn interface>HTMLDialogElement</dfn> : <span>HTMLElement</span> {
   element <var>dialog</var>:</p>
 
   <ol>
-   <li><p><span>Assert</span>: <var>dialog</var>'s
-   <span data-x="dialog-close-watcher">close watcher</span> is not null.</p></li>
+   <li><p><span>Assert</span>: <var>dialog</var>'s <span data-x="dialog-close-watcher">close
+   watcher</span> is null.</p></li>
 
    <li><p><span>Assert</span>: <var>dialog</var> has an <code data-x="attr-dialog-open">open</code>
    attribute and <var>dialog</var>'s <span>node document</span> is <span>fully active</span>.</p>