Mapped type over FormProps is `{[string]: any}` since 6.5.2

This commit https://github.com/final-form/react-final-form/issues/864 introduced a breaking change for TypeScript users because now mapped types over `FormProps` return a dictionary of `any`.

For example:
```ts
type FinalFormWrapperProps<
FormValues extends object = Record,
InitialFormValues = Partial
> = Omit, 'validate'>;
```
Result before this commit:

After:

TypeScript 4.0.3
final-form 4.20.1
react-final-form 6.5.2