Bump actions/download-artifact from 6 to 8

Bumps [actions/download-artifact](https://github.com/actions/download-artifact) from 6 to 8.
- [Release notes](https://github.com/actions/download-artifact/releases)
- [Commits](actions/download-artifact@v6...v8)

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

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

Author: dependabot[bot]

.github/workflows/run_scm_rts.yml

@@ -145,7 +145,7 @@ jobs:
         echo "artifact_id=${ARTIFACT_ID}" >> "$GITHUB_ENV"
 
     - name: Download SCM RT baselines
-      uses: actions/download-artifact@v6
+      uses: actions/download-artifact@v8
       with:
         name: rt-baselines-${{matrix.build-type}}-${{matrix.fortran-compiler}}-${{matrix.run_lists}}-main
         path: ${{ env.dir_bl }}