fix: markdown format for the blog-starter example (#37792)
fix: markdown format for the blog-starter example (#37792)

## Documentation / Examples

The markdown format for blog-starter example was broken, so fixed it.


- [x] Make sure the linting passes by running `pnpm lint`
  It failed, without my changes.
- [x] The examples guidelines are followed from [our contributing doc](https://github.com/vercel/next.js/blob/canary/contributing.md#adding-examples)

JeromeFitz/next.js,JeromeFitz/next.js,JeromeFitz/next.js,JeromeFitz/next.js