Combobox: investigate why dropdown opens upwards earlier than Select

Issue from escalation: https://github.com/grafana/support-escalations/issues/19629 Attachment: [myorg-combobox-panel.zip](https://github.com/user-attachments/files/25893234/myorg-combobox-panel.zip) Repro steps: 1. download the attached zip 2. extract the attached zip 3. cd to where you extracted the zip and run the following commands 3a. run npm install 3b. Make sure you don't have any running grafana instances on port 3000 3c. run npm run build && npm run server // starts a Grafana instance with a provisioned panel plugin 7. navigate to http://localhost:3000/d/a538aeff-5a8a-42a5-901c-938d896fdd6f/provisioned-combobox-dashboard 8. open dev tools on the bottom 9. expand / shrink the dev tools window until you notice how the Combobox dropdown opens upwards while the Select dropdown opens downwards 10. Investigate if this is possible to change 11. run docker compose down when you're done