Bump codecov/codecov-action from 3 to 4

Bumps [codecov/codecov-action](https://github.com/codecov/codecov-action) from 3 to 4.
- [Release notes](https://github.com/codecov/codecov-action/releases)
- [Changelog](https://github.com/codecov/codecov-action/blob/main/CHANGELOG.md)
- [Commits](codecov/codecov-action@v3...v4)

---
updated-dependencies:
- dependency-name: codecov/codecov-action
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>

.github/workflows/ci.yaml

@@ -42,7 +42,7 @@ jobs:
           pytest --cov=pygac_fdr pygac_fdr/tests --ignore=pygac_fdr/tests/test_end2end.py --cov-report=xml
 
       - name: Upload unittest coverage
-        uses: codecov/codecov-action@v3
+        uses: codecov/codecov-action@v4
         with:
           file: ./coverage.xml
           env_vars: OS,PYTHON_VERSION