Bump actions/download-artifact from 5 to 8

Bumps [actions/download-artifact](https://github.com/actions/download-artifact) from 5 to 8.
- [Release notes](https://github.com/actions/download-artifact/releases)
- [Commits](actions/download-artifact@v5...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/pr-preview.yml

@@ -19,15 +19,15 @@ jobs:
       actions: read
     steps:
       - name: Download generated site
-        uses: actions/download-artifact@v5
+        uses: actions/download-artifact@v8
         with:
           name: generated-site
           path: ./site
           run-id: ${{ github.event.workflow_run.id }}
           github-token: ${{ secrets.GITHUB_TOKEN }}
 
       - name: Download PR number
-        uses: actions/download-artifact@v5
+        uses: actions/download-artifact@v8
         with:
           name: pr-number
           run-id: ${{ github.event.workflow_run.id }}