upgrade: update actions/download-artifact action to v4

[renovate[bot]]

This PR contains the following updates:

Package	Type	Update	Change
actions/download-artifact	action	major	v3 -> v4

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Release Notes

actions/download-artifact (actions/download-artifact)

### [`v4`](https://togithub.com/actions/download-artifact/compare/v3...v4) [Compare Source](https://togithub.com/actions/download-artifact/compare/v3...v4)

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Configuration

📅 Schedule: Branch creation - "every weekend" in timezone Asia/Tokyo, Automerge - At any time (no schedule defined).

🚦 Automerge: Disabled by config. Please merge this manually once you are satisfied.

♻ Rebasing: Whenever PR becomes conflicted, or you tick the rebase/retry checkbox.

🔕 Ignore: Close this PR and you won't be reminded about this update again.

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• [ ] If you want to rebase/retry this PR, check this box

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This PR was generated by Mend Renovate. View the repository job log.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 97.52%. Comparing base (6765d3d) to head (ed61270).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #547 +/- ## ======================================= Coverage 97.52% 97.52% ======================================= Files 24 24 Lines 848 848 ======================================= Hits 827 827 Misses 21 21 ```

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[renovate[bot]]

Renovate Ignore Notification

Because you closed this PR without merging, Renovate will ignore this update. You will not get PRs for any future 4.x releases. But if you manually upgrade to 4.x then Renovate will re-enable minor and patch updates automatically.

If you accidentally closed this PR, or if you changed your mind: rename this PR to get a fresh replacement PR.