ArrowFunctionExpression returning ObjectPattern prints without parens when a return type is removed

I've created a minimal repro for this behavior here: https://github.com/conartist6/recast-arrow-object-pattern-repro

The input is:
```ts
(): Type => ({ prop: true });
```
and the output is invalid, as it is missing parens:
```
() => { prop: true };
```