Upload widget is being serialized to prompt

The upload widget is being serialized to prompt even though it shouldn’t be, resulting in a bogus `"choose file to upload": "image"` entry. From the look of it, the issue is the `serialize` property being set incorrectly here:

https://github.com/comfyanonymous/ComfyUI/blob/777f6b15225197898a5f49742682a2be859072d7/web/scripts/widgets.js#L364-L368

It should be:

```js
uploadWidget = node.addWidget("button", "choose file to upload", "image", () => {
fileInput.click();
}, {
serialize: false, // Don't include this in prompt.
});
```