Template: remove unnecessary conditions

Sry for the new PR, I removed the old fork...

The "is_ajax" conditions in the template file review-order.php are not necessary.
To move the html element to the form-checkout.php should also do the job.

PS: before you refer to #5910, please read also my comment below:
https://github.com/woothemes/woocommerce/pull/5910#issuecomment-50788660

Thanks :)