FIX: prevents open to happen too early (#26649)

In discourse-assign the assign menu in the modal is using this `expandedOnInsert` option and  was sometimes not opening correctly resulting in a broken state until you click two times on it. This should prevent this issue.

app/assets/javascripts/select-kit/addon/components/select-kit.js

@@ -198,7 +198,9 @@ export default Component.extend(
       this.appEvents.on("keyboard-visibility-change", this, this._updatePopper);
 
       if (this.selectKit.options.expandedOnInsert) {
-        this._open();
+        next(() => {
+          this._open();
+        });
       }
     },