docs: fix code block language in images-and-fonts docs (#73492)
## Summary
Update incorrect code block languages at [Images and
Fonts](https://nextjs.org/docs/canary/app/getting-started/images-and-fonts)
docs.
### 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
Co-authored-by: Delba de Oliveira <32464864+delbaoliveira@users.noreply.github.com>
