Bump actions/download-artifact from 3 to 4

Bumps [actions/download-artifact](https://github.com/actions/download-artifact) from 3 to 4.
- [Release notes](https://github.com/actions/download-artifact/releases)
- [Commits](https://github.com/actions/download-artifact/compare/v3...v4)

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

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

.github/workflows/publish.yml

@@ -38,7 +38,7 @@ jobs:
       - build-release
     steps:
       - name: fetch dists
-        uses: actions/download-artifact@v3
+        uses: actions/download-artifact@v4
         with:
           name: slither-dists
           path: dist/

.github/workflows/test.yml

@@ -109,7 +109,7 @@ jobs:
       - run: pip install coverage[toml]
 
       - name: download coverage data
-        uses: actions/download-artifact@v3.0.2
+        uses: actions/download-artifact@v4
         with:
           name: coverage-data