[Docs] fix example function param and signature (#51235)
Apparently the object deconstruction in the example doesn't work. This PR proposes a working version:
```diff
- export default function Page({ params: { slug: string } }) {
- return <div>My Post: {slug}</div>
- }
+ export default function Page({ params }: { params: { slug: string } }) {
+ return <div>My Post: {params.slug}</div>
+ }
```
According to the [page reference](https://nextjs.org/docs/app/api-reference/file-conventions/page), the page function parameter slugs needs to be retrieved by calling `params.slug`.
The TypeScript section below shows the correct function type signature, although not referencing to the parameter.
