DashboardSchema: Remove old unused legacy props style and timepicker.enable (#73879)

* DashboardScheam: Remove old unused legacy props style and timepicker.enable

* Update

* fix test

docs/sources/tutorials/provision-dashboards-and-data-sources/index.md

@@ -227,7 +227,6 @@ For more information on how to configure dashboard providers, refer to [Dashboar
      "refresh": "",
      "rows": [],
      "schemaVersion": 16,
-     "style": "dark",
      "tags": ["kubernetes"],
      "templating": {
        "list": []