build(deps): bump actions/download-artifact from 5 to 6

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] <support@github.com>

Author: dependabot[bot]

.github/workflows/tests.yml

@@ -70,7 +70,7 @@ jobs:
           sudo apt-get install -y --no-install-recommends llvm
 
       - name: Download artifacts
-        uses: actions/download-artifact@v5
+        uses: actions/download-artifact@v6
         with:
           name: cmake-build
 
@@ -120,7 +120,7 @@ jobs:
         uses: actions/checkout@v5
 
       - name: Download artifacts
-        uses: actions/download-artifact@v5
+        uses: actions/download-artifact@v6
         with:
           name: cmake-build