Bump actions/download-artifact from 4 to 8

Bumps [actions/download-artifact](https://github.com/actions/download-artifact) from 4 to 8.
- [Release notes](https://github.com/actions/download-artifact/releases)
- [Commits](https://github.com/actions/download-artifact/compare/v4...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>

.github/workflows/docs.yml

@@ -125,7 +125,7 @@ jobs:
            python3 mk_api_doc.py --js --go --output-dir=api --mld --z3py-package-path=../build-x64/python/z3 --build=../build-x64
 
       - name: Download Go Documentation
-        uses: actions/download-artifact@v8.0.0
+        uses: actions/download-artifact@v8
         with:
           name: go-docs
           path: doc/api/html/go/