Update cloud ClickHouse CI secrets to use _PROD suffix

[Copilot]

Summary

Updates CI workflow to use production-suffixed secrets for cloud ClickHouse instance credentials.

Changes:

• INTEGRATIONS_TEAM_TESTS_CLOUD_HOST_SMT → INTEGRATIONS_TEAM_TESTS_CLOUD_HOST_SMT_PROD
• INTEGRATIONS_TEAM_TESTS_CLOUD_PASSWORD_SMT → INTEGRATIONS_TEAM_TESTS_CLOUD_PASSWORD_SMT_PROD

Updated in both environment variable declarations and credential validation check in .github/workflows/tests.yaml.

Checklist

• CI configuration updated to reference correct production secrets

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