#### Fix parenthesis for optional function as return type (#11004, #19331 by @vjeux, @fisker)

<!-- prettier-ignore -->
```jsx
// Input
const fn = (a: number): ?((string) => string) => {
  return a > 0 ? (s) => `${s}: ${a}` : null;
};

// Prettier stable
const fn = (a: number): ?(string) => string => {
  return a > 0 ? (s) => `${s}: ${a}` : null;
};

// Prettier main
const fn = (a: number): ?((string) => string) => {
  return a > 0 ? (s) => `${s}: ${a}` : null;
};
```
