Bump codecov/codecov-action from 3.1.4 to 4.0.0 (#499)

Bumps [codecov/codecov-action](https://github.com/codecov/codecov-action) from 3.1.4 to 4.0.0.
- [Release notes](https://github.com/codecov/codecov-action/releases)
- [Changelog](https://github.com/codecov/codecov-action/blob/main/CHANGELOG.md)
- [Commits](codecov/codecov-action@v3.1.4...v4.0.0)

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

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

.github/workflows/ci.yaml

@@ -50,7 +50,7 @@ jobs:
  run: |
  pytest -n auto --cov=./ --cov-report=xml
  - name: Upload code coverage to Codecov
- uses: codecov/codecov-action@v3.1.4
+ uses: codecov/codecov-action@v4.0.0
  with:
  file: ./coverage.xml
  flags: unittests
@@ -114,7 +114,7 @@ jobs:
  run: |
  python -m mypy --install-types --non-interactive --cobertura-xml-report mypy_report cf_xarray/
  - name: Upload mypy coverage to Codecov
- uses: codecov/codecov-action@v3.1.4
+ uses: codecov/codecov-action@v4.0.0
  with:
  file: mypy_report/cobertura.xml
  flags: mypy