Add a noop onChange to remove react's warning

> Warning: Failed prop type: You provided a `value` prop to a form field without an `onChange` handler. This will render a read-only field. If the field should be mutable use `defaultValue`. Otherwise, set either `onChange` or `readOnly`.

src/TimePicker.jsx

@@ -285,6 +285,7 @@ export default class Picker extends Component {
             onFocus={onFocus}
             onBlur={onBlur}
             autoFocus={autoFocus}
+            onChange={noop}
           />
           <span className={`${prefixCls}-icon`}/>
         </span>