Revert "Bump codecov/codecov-action from 3 to 4 (#623)" (#624)

Author: hugovk

.github/workflows/ci.yml

@@ -33,7 +33,7 @@ jobs:
           python -m pip install tox
       - name: Run Tests
         run: tox -e py
-      - uses: codecov/codecov-action@v4
+      - uses: codecov/codecov-action@v3
         if: always()
         with:
           token: ${{ secrets.CODECOV_TOKEN }}