in a custom app getInitialProps the first own prop is [Function: withSuperJSON] instead of the value

### Verify Next.js canary release

- [X] I verified that the issue exists in the latest Next.js canary release

### Describe the bug

I'm trying to return props from a custom app getInitialProps function. But for some reason the first own property is always `[Function: withSuperJSON]` instead of the actual property.

Example here:
https://github.com/neotrow/next-superjson-test/blob/main/pages/_app.tsx#L30

### Expected behavior

I would expect the above mentioned console log to be
`ownProps { prop1: 'foo', prop2: 'bar', prop3: 'baz' }`
and not
`ownProps { prop1: [Function: withSuperJSON], prop2: 'bar', prop3: 'baz' }`

### Reproduction link

https://github.com/neotrow/next-superjson-test

### Version

0.5.9

### Config

```javascript
/** @type {import('next').NextConfig} */
const nextConfig = {
reactStrictMode: true,
experimental: {
swcPlugins: [["next-superjson-plugin", {}]],
},
};

module.exports = nextConfig;
```

### Additional context

_No response_