Fix big grid crashing due to missing React import

by fixing the cause rather than the symptom: this upgrades the code to use the new, recommended JSX transform mode of React 17+, which no longer requires you to import React manually just to write JSX.

src/form/Form.tsx

@@ -15,7 +15,7 @@ limitations under the License.
 */
 
 import classNames from "classnames";
-import React, { FormEventHandler, forwardRef, ReactNode } from "react";
+import { FormEventHandler, forwardRef, ReactNode } from "react";
 
 import styles from "./Form.module.css";