examples: remove `app-dir` in `i18n-routing` directory name (#73453)
### What?
1. Rename
[`app-dir-i18n-routing`](https://github.com/vercel/next.js/tree/canary/examples/app-dir-i18n-routing)
example `i18n-routing`.
2. Rename
[`i18n-routing`](https://github.com/vercel/next.js/tree/canary/examples/i18n-routing)
example `i18n-routing-pages`.
3. Update the docs mentions i18n-routing examples.
4. Update the test includes i18n-routing examples.
### Why?
The default has already been App Router anyways and a lot of examples
have migrated over.
x-ref:
https://github.com/vercel/next.js/pull/72642#issuecomment-2474415343
### How?
Change them as in
[reproduction-template](https://github.com/vercel/next.js/tree/canary/examples/reproduction-template)
and
[reproduction-template-pages](https://github.com/vercel/next.js/tree/canary/examples/reproduction-template-pages)
examples.
### 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
### Adding or Updating Examples
- [x] The "examples guidelines" are followed from our contributing doc
https://github.com/vercel/next.js/blob/canary/contributing/examples/adding-examples.md
- [x] Make sure the linting passes by running `pnpm build && pnpm lint`.
See
https://github.com/vercel/next.js/blob/canary/contributing/repository/linting.md
Co-authored-by: Delba de Oliveira <32464864+delbaoliveira@users.noreply.github.com>