github ci - use codecov github action @V3

adressing https://github.blog/changelog/2022-09-22-github-actions-all-actions-will-begin-running-on-node16-instead-of-node12/

.github/workflows/codecov.yml

@@ -22,7 +22,7 @@ jobs:
         pip install '.[tests]'
         pytest --cov=./ --cov-report=xml
     - name: Upload coverage to Codecov
-      uses: codecov/codecov-action@v2
+      uses: codecov/codecov-action@v3
       with:
         token: ${{ secrets.CODECOV_TOKEN }}
         directory: ./coverage/reports/