Update cloud ClickHouse JWT secret to use _PROD suffix

[Copilot]

Summary

Updates CI workflow JWT secret references to use the _PROD suffix, aligning with the existing HOST and PASSWORD secret naming convention for production cloud instances.

Changes

• Updated INTEGRATIONS_TEAM_TESTS_CLOUD_JWT_DESERT_VM_43 → INTEGRATIONS_TEAM_TESTS_CLOUD_JWT_DESERT_VM_43_PROD in:
  • .github/workflows/on_push.yml
  • .github/workflows/clickhouse_ci.yml

Checklist

• Unit and integration tests covering the common scenarios were added (N/A - configuration change only)
• A human-readable description of the changes was provided to include in CHANGELOG (N/A - internal CI configuration)
• For significant changes, documentation in https://github.com/ClickHouse/clickhouse-docs was updated with further explanations or tutorials (N/A - internal CI configuration)

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