Bump codecov/codecov-action from 5.3.1 to 6.0.0

Bumps [codecov/codecov-action](https://github.com/codecov/codecov-action) from 5.3.1 to 6.0.0.
- [Release notes](https://github.com/codecov/codecov-action/releases)
- [Changelog](https://github.com/codecov/codecov-action/blob/main/CHANGELOG.md)
- [Commits](codecov/codecov-action@v5.3.1...v6.0.0)

---
updated-dependencies:
- dependency-name: codecov/codecov-action
  dependency-version: 6.0.0
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

.github/workflows/codecov.yml

@@ -24,7 +24,7 @@ jobs:
           pytest -We tests
           lcov --capture --directory ./build/CMakeFiles/_PyPartMC.dir/ --output-file coverage.info --no-external
       - run: find -name \*.gcno | grep -v pypartmc.cpp | grep -v _PyPartMC.dir | xargs rm
-      - uses: codecov/codecov-action@v5.3.1
+      - uses: codecov/codecov-action@v6.0.0
         with:
           token: ${{ secrets.CODECOV_TOKEN }}
           fail_ci_if_error: true