Bump actions/download-artifact from 4 to 6

Bumps [actions/download-artifact](https://github.com/actions/download-artifact) from 4 to 6.
- [Release notes](https://github.com/actions/download-artifact/releases)
- [Commits](https://github.com/actions/download-artifact/compare/v4...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] <support@github.com>

.github/workflows/nuget-build.yml

@@ -165,7 +165,7 @@ jobs:
           python-version: '3.x'
       
       - name: Download all artifacts
-        uses: actions/download-artifact@v4
+        uses: actions/download-artifact@v6
         with:
           path: packages
       
@@ -220,7 +220,7 @@ jobs:
           python-version: '3.x'
       
       - name: Download x86 artifact
-        uses: actions/download-artifact@v4
+        uses: actions/download-artifact@v6
         with:
           name: windows-x86
           path: packages