LibJS+LibWeb: Use new Cell::Visitor helpers to avoid manual iteration

Author: https://github.com/awesomekling
Commit: 53d0dd4a2e
Pull-request: https://github.com/SerenityOS/serenity/pull/23971
Reviewed-by: https://github.com/trflynn89

Userland/Libraries/LibWeb/HTML/BrowsingContextGroup.cpp

@@ -35,8 +35,7 @@ void BrowsingContextGroup::visit_edges(Cell::Visitor& visitor)
 {
     Base::visit_edges(visitor);
     visitor.visit(m_page);
-    for (auto& context : m_browsing_context_set)
-        visitor.visit(context);
+    visitor.visit(m_browsing_context_set);
 }
 
 // https://html.spec.whatwg.org/multipage/document-sequences.html#creating-a-new-browsing-context-group-and-document