chore(examples): remove `with-windicss` example (#81846)
## Summary
Delete the entire
[with-windicss](https://github.com/vercel/next.js/tree/canary/examples/with-windicss)
directory and its contents
## Why?
[windicss](https://github.com/windicss/windicss) is
[sunsetting](https://windicss.org/posts/sunsetting.html).
## 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
cc: @samcx
Co-authored-by: Joseph <joseph.chamochumbi@vercel.com>
