Fix `message` PropType of `ActionableMessage` (#9653)

The `message` prop of `ActionableMessage` had a PropType of `string`,
but it was being passed a `node`. This was resulting in a PropType
error in the console on the view quote page.

The PropType has been changed to `node`, and the error is now gone.

ui/app/pages/swaps/actionable-message/actionable-message.js

@@ -38,7 +38,7 @@ export default function ActionableMessage ({
 }
 
 ActionableMessage.propTypes = {
-  message: PropTypes.string.isRequired,
+  message: PropTypes.node.isRequired,
   primaryAction: PropTypes.shape({
     label: PropTypes.string,
     onClick: PropTypes.func,