None of the codesandbox examples work

This applies to all of the examples, when clicking the Codesandbox link it fails to build with an error.
Error from [this example](https://github.com/keystonejs/keystone/tree/main/examples/usecase-blog) is the following:

```
yarn run v1.22.19
$ keystone dev
✨ Starting Keystone
✘ [ERROR] Could not resolve "../example-utils"

keystone.ts:2:30:
2 │ import { fixPrismaPath } from '../example-utils';
╵ ~~~~~~~~~~~~~~~~~~

error Command failed with exit code 1.
info Visit https://yarnpkg.com/en/docs/cli/run for documentationabout this command.
```

Codesandbox link:
https://githubbox.com/keystonejs/keystone/tree/main/examples/usecase-blog

Start by inspecting examples/usecase-blog/keystone.ts and its ../example-utils import, then reproduce the failure through the provided Codesandbox link. Done means the Codesandbox build succeeds for this example and the same fix works across the other examples.

Written by the indexing model from the issue text.