[css-fonts-4][editorial] dedup ids on examples

Author: svgeesus

css-fonts-4/Overview.bs

@@ -1044,7 +1044,7 @@ Font width: the 'font-width!!property' property</h3>
 		becomes set to 'condensed'.
 	</div>
 
-	<div class="example" id="ex-font-stretch-set">
+	<div class="example" id="ex-font-width-set">
 		For example, here the 'font-width!!property' is used
 		on level one headings.