WidgetBaseInterface::formElement documentation does not match method signature

The docblock for WidgetBaseInterface::formElement() has "@param string $form" and "@param string $form_state" but the method signature is as follows.

public function formElement(FieldItemListInterface $items, $delta, array $element, array &$form, array &$form_state);

Both $form and $form_state are array's not strings.

The attached patch fixes this in the docblock and also converts two instances of "subelements" to "sub-elements" in the same docblock.