That looks like the OOTB icon that comes with the helper text. You can try overriding where/what font family is being used for this CSS class. I believe it will be the Pega Icons coming from the UI-Kit if I am not mistaken.
However, that might be harder than another approach.
Have you considered just adding your own icon to your form? This way you will have a lot more control over what is being displayed and also the actions which could be configured on it?