Editorial: fix typo in system focus check

Author: jan-ivar

source

@@ -73492,7 +73492,7 @@ END:VCARD</pre>
 
   <ol>
    <li><p>If <var>target</var>'s <span data-x="concept-document-bc">browsing context</span>'s
-   <span>top-level browsing context</span> does have not have <span data-x="tlbc system
+   <span>top-level browsing context</span> does not have <span data-x="tlbc system
    focus">system focus</span>, then return false.</p></li>
 
    <li><p>Let <var>candidate</var> be <var>target</var>'s <span>top-level browsing context</span>'s