app crushes when any prop from FormState is passed as a prop to FormProps

### **bug report**

### What is the current behavior?

If I pass any prop from the [FormState](https://final-form.org/docs/final-form/types/FormState) to the Form instances:
```
import * as React from "react";
import { Form, Field } from "react-final-form";

const F = () => {
return ;
};

export default function App() {
return (
{}}
initialValues={{ x: "xxx", foo: "bar" }}
/>
);
}
```

The form crushes with:
```
TypeError
Cannot set property active of # which has only a getter
```

### What is the expected behavior?

I'd expect the form to ignore prop not present in the FormProps.

### Sandbox Link

https://codesandbox.io/s/active-prop-bug-8qrcw?file=/src/App.tsx

### What's your environment?

final-form@4.20
react-final-form@6.5.0