[css-values-5][editorial] Fix markup

Author: tabatkins

css-values-5/Overview.bs

@@ -3522,7 +3522,7 @@ calc-size/interpolate-size-parsing.html
 	The [=calc-size basis=] values are:
 
 	<dl dfn-type=value dfn-for="calc-size()">
-		: <dfn>&lt;size-keyword</dfn>
+		: <dfn type>&lt;size-keyword></dfn>
 		::
 			Indicates that the ''calc-size()'' is basing its size off of the specified keyword.
 			Represents any sizing keywords allowed in the context