[css-highlight-api] Fix typo

Author: frivoal

css-highlight-api-1/Overview.bs

@@ -468,7 +468,7 @@ Range Updating and Invalidation</h3>
 	if [=start node=] or [=end node=] of any [=range=]
 	in the [=highlight regsitry=]
 	refer to a {{Node}} which is no longer [=in a document tree=],
-	the User Agent must ignored that [=range=].
+	the User Agent must ignore that [=range=].
 	If the [=start offset=] or [=end offset=] of any [=range=]
 	are greater than the corresponding node’s <a spec=dom>length</a>,
 	The User Agent must behave as if it was equal to that <a spec=dom>length</a>.