Fix coverage conversion to xml before upload

Author: astanziola

.github/workflows/tests.yml

@@ -20,8 +20,10 @@ jobs:
       - name: Running tests
         run: poetry run coverage run --source=jaxdf -m pytest -xvs
       - name: Install coverage
-        run: pip install coverage
-      - name: "Upload combined coverage to Codecov"
+        run: |
+          pip install coverage
+          coverage xml
+      - name: "Upload coverage to Codecov"
         uses: codecov/codecov-action@v3
         with:
           token: ${{ secrets.CODECOV_TOKEN }}