upgrade: update actions/upload-artifact action to v4 (#573)

This PR contains the following updates:

| Package | Type | Update | Change |
|---|---|---|---|
|
[actions/upload-artifact](https://redirect.github.com/actions/upload-artifact)
| action | major | `v3` -> `v4` |

---

### Release Notes

<details>
<summary>actions/upload-artifact (actions/upload-artifact)</summary>

###
[`v4`](https://redirect.github.com/actions/upload-artifact/compare/v3...v4)

[Compare
Source](https://redirect.github.com/actions/upload-artifact/compare/v3...v4)

</details>

---

### Configuration

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Asia/Tokyo, Automerge - At any time (no schedule defined).

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

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rebase/retry checkbox.

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

---

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---

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.github/workflows/release.yml

@@ -68,7 +68,7 @@ jobs:
         env:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
 
-      - uses: actions/upload-artifact@v3
+      - uses: actions/upload-artifact@v4
         with:
           name: sha256
           path: packages/command/bin/${{ matrix.target }}/fluttergen-${{ matrix.artifact_prefix }}.sha256