Fix test that was converted to story incorrectly

Author: React-Admin CI

packages/ra-ui-materialui/src/input/DateInput.spec.tsx

@@ -79,7 +79,7 @@ describe('<DateInput />', () => {
             <Basic
                 simpleFormProps={{
                     onSubmit,
-                    defaultValues: { publishedAt: '2021-09-11' },
+                    defaultValues: { publishedAt: new Date('2021-09-11') },
                 }}
             />
         );