CI(dependabot): Bump codecov/codecov-action from 3 to 4 (#109)

* CI(dependabot): 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] <support@github.com>

* CI: Add CodeCov token

---------

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Adrien Berchet <adrien.berchet@epfl.ch>

.github/workflows/run-tox.yml

@@ -67,12 +67,13 @@ jobs:
       with:
         report_paths: 'reports/pytest-*.xml'
     - name: Upload to codecov
-      uses: codecov/codecov-action@v3
+      uses: codecov/codecov-action@v4
       with:
         fail_ci_if_error: false
         directory: ./reports
         flags: pytest
         name: "luigi-tools-py${{ matrix.python-version }}-${{ matrix.min_versions }}"
+        token: ${{ secrets.CODECOV_TOKEN }}
     - name: Upload test artifacts
       uses: actions/upload-artifact@v4
       if: always()