Fix "Failed prop type: DateTimePicker: prop type portalContainer is invalid" error

Author: wojtekmaj

src/DateTimePicker.tsx

@@ -662,7 +662,6 @@ DateTimePicker.propTypes = {
   onClockOpen: PropTypes.func,
   onFocus: PropTypes.func,
   openWidgetsOnFocus: PropTypes.bool,
-  portalContainer: isBrowser ? PropTypes.instanceOf(HTMLElement) : undefined,
   required: PropTypes.bool,
   secondAriaLabel: PropTypes.string,
   secondPlaceholder: PropTypes.string,
@@ -672,4 +671,8 @@ DateTimePicker.propTypes = {
   yearPlaceholder: PropTypes.string,
 };
 
+if (isBrowser) {
+  DateTimePicker.propTypes.portalContainer = PropTypes.instanceOf(HTMLElement);
+}
+
 export default DateTimePicker;