Remove improper assert in dialog show

Author: keithamus

source

@@ -62628,9 +62628,6 @@ interface <dfn interface>HTMLDialogElement</dfn> : <span>HTMLElement</span> {
    <li><p>Add an <code data-x="attr-dialog-open">open</code> attribute to <span>this</span>, whose
    value is the empty string.</p></li>
 
-   <li><p><span>Assert</span>: <span>this</span>'s <span data-x="dialog-close-watcher">close
-   watcher</span> is not null.</p></li>
-
    <li><p>Set <span>this</span>'s <span>previously focused element</span> to the
    <span>focused</span> element.</p></li>