test: verify K8S CI runner Docker Hub connectivity

[srchilukoori]

Summary

Test PR to verify whether K8S CI job CeleryExecutor-3.11-v1.31.12-true has a persistent Docker Hub connectivity issue.

Context

PR #65840 consistently fails on Kubernetes tests / K8S System:CeleryExecutor-3.11-v1.31.12-true with:

docker: Error response from daemon: Head "https://registry-1.docker.io/v2/library/bash/manifests/latest": net/http: TLS handshake timeout

This occurs at the workspace cleanup step before any code runs. Multiple re-runs produce the same failure. This PR contains a no-op comment addition to trigger the full K8S matrix and confirm whether the issue is systemic.

Expected outcome

• If CeleryExecutor-3.11-v1.31.12-true fails here too → infra issue, not PR-specific
• If it passes → issue was transient or specific to Add sphinx-airflow-theme as uv workspace member #65840's runner allocation

Will close this PR after CI completes regardless of outcome.

Changes

No functional changes. Comment-only edit to .github/workflows/k8s-tests.yml.