s/Level 3/Level 4 (w3c#5318)

Now that Level 5 includes all of Level 4, this can be updated in the abstract also

Author: tantek

mediaqueries-5/Overview.bs

@@ -15,7 +15,7 @@ Editor: Florian Rivoal, Invited Expert, https://florian.rivoal.net, w3cid 43241
 Editor: Tab Atkins Jr., Google, http://xanthir.com/contact/, w3cid 42199
 Abstract: <a>Media Queries</a> allow authors to test and query values or features of the user agent or display device, independent of the document being rendered.  They are used in the CSS @media rule to conditionally apply styles to a document, and in various other contexts and languages, such as HTML and JavaScript.
 
-	Media Queries Level 5 describes the mechanism and syntax of media queries, media types, and media features. It extends and supersedes the features defined in Media Queries Level 3.
+	Media Queries Level 5 describes the mechanism and syntax of media queries, media types, and media features. It extends and supersedes the features defined in Media Queries Level 4.
 Include MDN Panels: no
 </pre>