[css-flexbox-1] Adjust wording after removal of min-width/height: auto propdef box per #2103

Author: fantasai

css-flexbox-1/Overview.bs

@@ -892,19 +892,21 @@ Collapsed Items</h3>
 <h3 id="min-size-auto">
 Automatic Minimum Size of Flex Items</h3>
 
-	To provide a more reasonable default minimum size for <a>flex items</a>,
-	this specification introduces a new ''min-width/auto'' value
-	as the initial value of the 'min-width' and 'min-height' properties defined in CSS 2.1. [[!CSS21]]
+	Note: The ''min-width/auto'' value of 'min-width' and 'min-height' is new.
+	It was initially introduced as the new initial value of these properties
+	in this specification;
+	its formal definition has now been moved
+	to the <a href="http://www.w3.org/TR/css-sizing/">CSS Sizing</a> module.
+	It is still required for a complete and correct implementation
+	of this module.
 
-	<dl>
-		<dt>''min-width/height: auto''
-		<dd>
-			On a <a>flex item</a> whose 'overflow' is ''overflow/visible'' in the <a>main axis</a>,
-			when specified on the <a>flex item's</a> main-axis min-size property,
-			specifies an <a>automatic minimum size</a>.
-			Otherwise computes to ''0''
-			(unless otherwise defined by a future specification).
-	</dl>
+	To provide a more reasonable default minimum size for <a>flex items</a>,
+	this specification defines that the ''min-width/auto'' keyword
+	of the 'min-width' and 'min-height' properties
+	(which represents their initial value)
+	applies an <a>automatic minimum size</a>
+	to <a>flex items</a> whose 'overflow' is ''overflow/visible'' in the <a>main axis</a>.
+	(It otherwise computes to zero, see [[!CSS3-SIZING]].)
 
 	In general, the <a>automatic minimum size</a> of a <a>flex item</a>
 	is the smaller of its <a>content size</a> and its <a>specified size</a>.