Unfortunately, it's not possible to configure message box size in the method "showInformationDialog". However you can resize the message box by applying custom css. The article by the link below describes how to add custom css style:

https://community.creatio.com/articles/how-add-or-edit-css-style

The example for css style:

.ts-messagebox-box {

    height: 500px;

    width: 500px;

}

Please note that this css style can be applied globally, to all message boxes in the system.