Fix invalid markdown lang (#41926)
Fix invalid markdown lang (#41926)

## Documentation / Examples

- [x] Make sure the linting passes by running `pnpm lint`
- [x] The "examples guidelines" are followed from [our contributing
doc](https://github.com/vercel/next.js/blob/canary/contributing/examples/adding-examples.md)
JeromeFitz/next.js,JeromeFitz/next.js,JeromeFitz/next.js,JeromeFitz/next.js