I believe that my first suggestion would only remove the message, which is why I deleted my comment and did some digging.
There are add/remove action/filter functions in the JS. You might want to take a look at the file /assets/js/input.js and this document http://www.advancedcustomfields.com/resources/adding-custom-javascript-fields/. You may be able to find something where I didn’t. If that is done by an action it should be possible to remove the action.
