[css-display-3] Fix markup error.

Author: fantasai

css-display-3/Overview.bs

@@ -1791,8 +1791,8 @@ Changes</h2>
 			Clarified that [=blockification=] and [=inlinification=] are [=computed value=] changes.
 			(<a href="https://github.com/w3c/csswg-drafts/issues/6251">Issue 6251</a>)
 			<blockquote>
-				<p>Some layout effects require <dfn export lt="blockify|blockification">blockification</dfn>
-				or <dfn export lt="inlinify|inlinification">inlinification</dfn> of the box type,
+				<p>Some layout effects require [=blockification=]
+				or [=inlinification=] of the box type,
 				which sets the box’s <ins>[=computed value|computed=]</ins> <a>outer display type</a>
 				to ''block'' or ''inline'' (respectively).
 			</blockquote>