[css-nav-1] Fix a link error

Author: Jihye Hong

css-nav-1/Overview.bs

@@ -1080,7 +1080,7 @@ they must not be set differently.
 
 <div algorithm="to set the search origin">
 
-To <dfn lt="set the search origin | setting the search origin">set the search origin</dfn>,
+To <dfn lt="set the search origin | setting the search origin">set the <a>search origin</a></dfn>,
 run the following steps:
 
 1. Let <var>searchOrigin</var> be the <a>DOM anchor</a> of the <a>currently focused area of a top-level browsing context</a>.