Merge pull request #522 from stan-dev/dependabot/github_actions/codecov/codecov-action-6

Bump codecov/codecov-action from 5 to 6

Author: jgabry

.github/workflows/test-coverage.yaml

@@ -40,7 +40,7 @@ jobs:
           covr::to_cobertura(cov)
         shell: Rscript {0}
 
-      - uses: codecov/codecov-action@v5
+      - uses: codecov/codecov-action@v6
         with:
           # Fail if error if not on PR, or if on PR and token is given
           fail_ci_if_error: ${{ github.event_name != 'pull_request' || secrets.CODECOV_TOKEN }}