[css-align] s/auto/legacy/ to fix stray reference per w3c#1449

Author: fantasai

css-align/Overview.bs

@@ -1464,7 +1464,7 @@ Self-Alignment Shorthand: the 'place-items' property</h3>
 
 	<pre class="propdef">
 	Name: place-items
-	Value: [ normal | stretch | <<baseline-position>> | <<self-position>> ] [ auto | normal | stretch | <<baseline-position>> | <<self-position>> ]?
+	Value: [ normal | stretch | <<baseline-position>> | <<self-position>> ] [ normal | stretch | <<baseline-position>> | <<self-position>> ]?
 	Initial: see individual properties
 	Applies to: all elements
 	Inherited: no