examples: remove `with-styled-components-babel` (#73229)
## Description
Follow up [the
comment](https://github.com/vercel/next.js/pull/70663#issuecomment-2389724843)
in #70663.
> Let's go ahead and remove these Babel `style-jsx-...` examples. It's
getting an error, and it's likely not worth the effort to fix/keep
around as an example.
In addition,
[with-styled-components-babel](https://github.com/vercel/next.js/tree/canary/examples/with-styled-components-babel)
example is no longer needed because the simple [with-styled-components
example](https://github.com/vercel/next.js/tree/canary/examples/with-styled-components)
exists.
CC: @samcx
### 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: Sam Ko <sam@vercel.com>
