Bump codecov/codecov-action from 5 to 6

Bumps [codecov/codecov-action](https://github.com/codecov/codecov-action) from 5 to 6.
- [Release notes](https://github.com/codecov/codecov-action/releases)
- [Changelog](https://github.com/codecov/codecov-action/blob/main/CHANGELOG.md)
- [Commits](codecov/codecov-action@v5...v6)

---
updated-dependencies:
- dependency-name: codecov/codecov-action
  dependency-version: '6'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

.github/workflows/tox.yml

@@ -50,7 +50,7 @@ jobs:
         PYTHON_ENV="py$(echo $PYTHON_VERSION | sed 's/\.//;s/\-dev//')"
         tox -e "${PYTHON_ENV}-${PANDAS_PRESENCE}"
     - name: Upload coverage to Codecov
-      uses: codecov/codecov-action@v5
+      uses: codecov/codecov-action@v6
       with:
         files: ./coverage.xml
         flags: unittests