[css-box] Fix bikeshed error

Author: fantasai

css-box-3/Overview.bs

@@ -135,7 +135,7 @@ The CSS Box Model {#box-model}
 
 	The perimeter of each of the four areas
 	(content, padding, border, and margin)
-	is called an <dfn export lt="box edge | edge" for="box" local-lt="edge">edge</dfn>,
+	is called an <dfn export lt="box edge | edge" for="box">edge</dfn>,
 	and each [=edge=] can be broken down into
 	a top, right, bottom, and left side.
 	Thus each <a>box</a> has four [=edges=]

css-box-4/Overview.bs

@@ -124,7 +124,7 @@ The CSS Box Model {#box-model}
 
 	The perimeter of each of the four areas
 	(content, padding, border, and margin)
-	is called an <dfn export lt="box edge | edge" for="box" local-lt="edge">edge</dfn>,
+	is called an <dfn export lt="box edge | edge" for="box">edge</dfn>,
 	and each [=edge=] can be broken down into
 	a top, right, bottom, and left side.
 	Thus each <a>box</a> has four [=edges=]