Set top 10 list to be not clearable via dropdown.

src/aki_prj23_transparenzregister/ui/pages/home.py

@@ -194,6 +194,7 @@ def layout() -> html:
                                     id="dropdown_table_metric",
                                     className="dropdown-style",
                                     persistence=True,
+                                    clearable=False,
                                 ),
                             ],
                         ),