docs: add correct switcher to partial prerendering docs (#68418)
## For Contributors
### Improving Documentation
- [x] Run `pnpm prettier-fix` to fix formatting issues before opening
the PR.
- [x] Read the Docs Contribution Guide to ensure your contribution
follows the docs guidelines:
https://nextjs.org/docs/community/contribution-guide
### What?
Add switchers of `next.config.js` and `next.config.ts`.
In addition, insert some commas.
### Why?
Config file type isn't same in the [PPR
docs](https://rc.nextjs.org/docs/app/building-your-application/rendering/partial-prerendering).
### How?
N/A
x-ref: #68210
---------
Co-authored-by: Delba de Oliveira <32464864+delbaoliveira@users.noreply.github.com>