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] <[email protected]>

Author: dependabot[bot]

.github/workflows/linux.yml

@@ -83,7 +83,7 @@ jobs:
     timeout-minutes: 60
     steps:
       - name: Download code coverage results
-        uses: actions/download-artifact@v5
+        uses: actions/download-artifact@v6
       - run: |
           echo 'mode: atomic' > summary.txt
           tail -q -n +2 *.out >> summary.txt