Bump actions/download-artifact from 3 to 4.1.7 in /.github/workflows

Bumps [actions/download-artifact](https://github.com/actions/download-artifact) from 3 to 4.1.7.
- [Release notes](https://github.com/actions/download-artifact/releases)
- [Commits](actions/download-artifact@v3...v4.1.7)

---
updated-dependencies:
- dependency-name: actions/download-artifact
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

.github/workflows/build_bookdown.yaml

@@ -46,7 +46,7 @@ jobs:
       uses: actions/checkout@v3
       with: 
         ref: ${{github.ref}}
-    - uses: actions/download-artifact@v3
+    - uses: actions/download-artifact@v4.1.7
       with: 
         name: site
         path: site/