[Example] with-react-intl: fix doubling messages (#17175)
[Example] with-react-intl: fix doubling messages (#17175)

Because `import()` for .json files return object like this:

```json
{
  "default": {
     "some": ...
  },
 "some": ...
}
```

![image](https://user-images.githubusercontent.com/2598671/93468826-4156b200-f8f8-11ea-8e39-42df2df83057.png)

JeromeFitz/next.js,azukaru/next.js,zeit/next.js,azukaru/next.js,zeit/next.js,flybayer/next.js,flybayer/next.js,JeromeFitz/next.js,flybayer/next.js,JeromeFitz/next.js,zeit/next.js,JeromeFitz/next.js,azukaru/next.js,flybayer/next.js,azukaru/next.js