The accept / reject / ignore workflow is pretty central to Prodigy, so I normally wouldn't recommend disabling the "ignore" option and not giving the user an option to skip a question. However, if you need it for your specific use case, you can always hide and/or disable the button via the global_css. I've posted an example of disabling the reject button here:
“nth-child” refers to the “nth” child of the buttons container. The red button is the second, hence nth-child(2). The ignore button is the third, so it’d be nth-child(3).