MAINT: Revert actions/download-artifact@v4 to @V3

Author: MartinThoma

.github/workflows/github-ci.yaml

@@ -201,7 +201,7 @@ jobs:
 
       - run: python -m pip install --upgrade coverage[toml]
 
-      - uses: actions/download-artifact@v4
+      - uses: actions/download-artifact@v3
         with:
           name: coverage-data