[css-ui-4] Delete stray text in example

Author: frivoal

css-ui-4/Overview.bs

@@ -1980,7 +1980,7 @@ was composed of multiple elements or pseudo-elements combined together.
 <div class=example>
 	For example, the [[HTML]] <{select}> element is often rendered with an arrow on the right side
 	indicating that the list will be expanded if the element is clicked.
-	If the computed value of 'appearance' on a <{select}> element is ''appearance/none'' or ''appearance/button'',
+	If the computed value of 'appearance' on a <{select}> element is ''appearance/none''
 	this must disappear.
 </div>