Remove automated EKS release path

[suguanYang]

Summary

• Remove the EKS staging rollback dispatch input and all EKS migration/deployment jobs.
• Remove EKS-specific CI configuration and make release completion depend only on ECS production.
• Keep ECS staging and production deployment paths unchanged.

Validation

• YAML parsing and job dependency graph validation passed.
• git diff --check passed.
• CI workflow scan contains no EKS deployment, Kubernetes, or rollback path.

Related: Ontos-AI/knowhere-api-infra#19 and #26.

No AWS resources were changed.