[cssom-view-1] Whoops, forgot arg name.

Author: tabatkins

cssom-view-1/Overview.bs

@@ -1047,7 +1047,7 @@ partial interface Element {
   DOMRectList getClientRects();
   [NewObject] DOMRect getBoundingClientRect();
 
-  bool isVisible(optional IsVisibleOptions = {});
+  bool isVisible(optional IsVisibleOptions options = {});
 
   undefined scrollIntoView(optional (boolean or ScrollIntoViewOptions) arg = {});
   undefined scroll(optional ScrollToOptions options = {});