[css-content-3] Fix initial value of quotes to be auto. #4074

Author: fantasai

css-content-3/Overview.bs

@@ -382,7 +382,7 @@ Specifying quotes with the 'quotes' property</h4>
 	<pre class='propdef'>
 		Name: quotes
 		Value: auto | none | [ <<string>> <<string>> ]+
-		Initial: depends on user agent
+		Initial: auto
 		Applies To: all elements
 		Inherited: yes
 		Percentages: n/a