[css-highlights-api] Markup fix

Author: frivoal

css-highlight-api-1/Overview.bs

@@ -223,8 +223,8 @@ Registering Custom Highlights</h3>
 		invoke the <code>set</code> method of the [=highlight registry=]
 		which will run [[webidl#es-map-set|the steps for a built-in maplike set function]],
 		with the [=context object=] as the <code>this</code> value,
-		the passed-in [=custom highlight name=] as |keyArg|,
-		and the passed-in highlight as |valueArg|.
+		the passed-in [=custom highlight name=] as <var ignore>keyArg</var>,
+		and the passed-in highlight as <var ignore>valueArg</var>.
 
 		The <dfn>custom highlight name</dfn> assigned to a [=custom highlight=] when it is [=registered=]
 		is used to identify the highlight during styling (see [[#styling-highlights]]).