Bump actions/download-artifact from 2 to 4.1.7 in /.github/workflows

Bumps [actions/download-artifact](https://github.com/actions/download-artifact) from 2 to 4.1.7.
- [Release notes](https://github.com/actions/download-artifact/releases)
- [Commits](https://github.com/actions/download-artifact/compare/v2...v4.1.7)

---
updated-dependencies:
- dependency-name: actions/download-artifact
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

.github/workflows/build-signed-deb.yml

@@ -60,7 +60,7 @@ jobs:
     - uses: actions/checkout@v2
 
     - name: 'Download Unsigned Packages'
-      uses: actions/download-artifact@v2
+      uses: actions/download-artifact@v4.1.7
       with:
         name: DebianUnsigned
         path: tosign