fix: add missing opened styles to ported combo-box CSS (#9358)

Author: web-padawan

packages/vaadin-lumo-styles/src/components/combo-box.css

@@ -3,6 +3,10 @@
  * Copyright (c) 2017 - 2025 Vaadin Ltd.
  * This program is available under Apache License Version 2.0, available at https://vaadin.com/license/
  */
+:host([opened]) {
+  pointer-events: auto;
+}
+
 [part='toggle-button']::before {
   content: var(--lumo-icons-dropdown);
 }