Bump @cloudflare/vitest-pool-workers from 0.2.12 to 0.4.0

Bumps [@cloudflare/vitest-pool-workers](https://github.com/cloudflare/workers-sdk/tree/HEAD/packages/vitest-pool-workers) from 0.2.12 to 0.4.0.
- [Release notes](https://github.com/cloudflare/workers-sdk/releases)
- [Changelog](https://github.com/cloudflare/workers-sdk/blob/main/packages/vitest-pool-workers/CHANGELOG.md)
- [Commits](https://github.com/cloudflare/workers-sdk/commits/@cloudflare/[email protected]/packages/vitest-pool-workers)

---
updated-dependencies:
- dependency-name: "@cloudflare/vitest-pool-workers"
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]