Optional record fields rendered incorrectly in type errors

E.g.:

A.res:
```rescript
type a = {x?: string}
```

A.resi:
```rescript
type a = {y?: string}
```

=>

```
    Type declarations do not match:
         type rec a = {?x: string}
       is not included in
         type rec a = {?y: string}
```

It should be `x?: string`, not `?x: string`.

And isn't `rec` incorrect, too?