build(deps): bump actions/download-artifact from 4 to 8 (#7614)

Bumps [actions/download-artifact](https://github.com/actions/download-artifact) from 4 to 8.
- [Commits](https://github.com/actions/download-artifact/compare/v4...v8)

---
updated-dependencies:
- dependency-name: actions/download-artifact
  dependency-version: '8'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

.github/workflows/deb-package.yml

@@ -203,7 +203,7 @@ jobs:
     permissions:
       contents: write
     steps:
-      - uses: actions/download-artifact@v4
+      - uses: actions/download-artifact@v8
         with:
           path: dist
           pattern: etherpad-*-deb