Fix typo in Overview.bs (#11964)

Author: Psychpsyo

Diff for: cssom-1/Overview.bs

@@ -3062,7 +3062,7 @@ steps:
  <li>If <var>pseudoElt</var> is provided, is not the empty string, and starts with a colon, then:
   <ol>
     <li>[=CSS/Parse=] <var>pseudoElt</var> as a <<pseudo-element-selector>>, and let <var>type</var> be the result.
-    <li>If <var>type</var> is failure, or is an ''::slotted()'' or ''::part()'' pseudo-element, let <var>obj</var> be null.
+    <li>If <var>type</var> is failure, or is a ''::slotted()'' or ''::part()'' pseudo-element, let <var>obj</var> be null.
     <li>Otherwise let <var>obj</var> be the given pseudo-element of <var>elt</var>.
   </ol>