build(deps): 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](https://github.com/codecov/codecov-action/compare/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>

.github/workflows/ci.yml

@@ -75,7 +75,7 @@ jobs:
       - uses: actions/setup-go@v6
         with: { go-version: '1.25' }
       - run: make test-coverage
-      - uses: codecov/codecov-action@v5
+      - uses: codecov/codecov-action@v6
         with:
           files: ./coverage.out
           token: ${{ secrets.CODECOV_TOKEN }}