Documentation for defaultValue of FieldProps is not matching implementation

### Are you submitting a **bug report** or a **feature request**?

**bug report**

### What is the current behavior?

The documentation for [Field defaultValue](https://final-form.org/docs/react-final-form/types/FieldProps) states:

>The value of the field upon creation. This value is only needed if you want your field be dirty upon creation (i.e. for its ***value to be different from its initial value***).

So assumption is that to mark **field as initially dirty** we can set different defaultValue and initialValue.

For example:

```

```

### What is the expected behavior?

Field defaultValue is only used when both form and field level **initialValue are undefined.** thus Field is not marked dirty, when initialValue is not undefined.

Current implementation:
https://github.com/final-form/final-form/blob/main/src/FinalForm.js#L908

```
// only use defaultValue if we don't yet have any value for this field
if (
fieldConfig.defaultValue !== undefined &&
fieldConfig.initialValue === undefined &&
getIn(state.formState.initialValues, name) === undefined &&
noValueInFormState
) {
state.formState.values = setIn(
state.formState.values,
name,
fieldConfig.defaultValue,
);
}
```

### Sandbox Link

### What's your environment?

React Final Form: 6.5.9

### Other information