ci: bump actions/download-artifact from 5 to 6 (#31)

Bumps [actions/download-artifact](https://github.com/actions/download-artifact) from 5 to 6.
- [Release notes](https://github.com/actions/download-artifact/releases)
- [Commits](actions/download-artifact@v5...v6)

---
updated-dependencies:
- dependency-name: actions/download-artifact
  dependency-version: '6'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

.github/workflows/publish.yml

@@ -62,7 +62,7 @@ jobs:
           VERSION=$(awk -F'[<>]' '/^[[:space:]]*<Version>/ {print $3}' QsNet/QsNet.csproj)
           echo "VERSION=$VERSION" >> $GITHUB_ENV
       - name: Download package artifact
-        uses: actions/download-artifact@v5
+        uses: actions/download-artifact@v6
         with:
           name: QsNet.${{ env.VERSION }}
           path: ./artifacts

.github/workflows/test.yml

@@ -265,7 +265,7 @@ jobs:
     steps:
       - uses: actions/checkout@v5
       - name: Download nupkg
-        uses: actions/download-artifact@v5
+        uses: actions/download-artifact@v6
         with:
           name: qsnet-nupkg
           path: ./nupkg