ci: remove obsolete review cleanup workflow

[JOY (JOY)]

Summary

• remove the disabled upstream review cleanup workflow
• avoid reactivating cleanup jobs that target Blockscout Vault, Kubernetes, and private image infrastructure
• remove the invalid pull request activity type reported by actionlint

Evidence

• workflow ID 90425999 is disabled manually
• the review deployment workflow has no recorded runs in this fork
• cleanup run 29305460310 failed against vault.k8s.blockscout.com with HTTP 400
• Docker cleanup jobs in the same run failed because the required token input was missing

Validation

• git diff --check
• confirmed no remaining cleanup workflow references under .github
• full actionlint still reports unrelated pre-existing findings in checks.yml, publish-image.yml, and stale-issues.yml