I’m having a bit of trouble figuring out why anyone might want this. Best practice in web design is always to allow the user to correct a mistake.
If you can explain the circumstances in which it might be needed, I could consider adding such an option, but I’d need to know just how it would be used.
Meantime, if you really need to hide the button on all your open webforms, you could add this to your theme style.css file:
button[id^=”ewz_change_”]{display: none;}