Suppress warnings in config template

[JimMadge]

✅ Checklist

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🚦 Depends on

⤴️ Summary

🌂 Related issues

Closes #1838

🔬 Tests

[github-actions]

Coverage report

Click to see where and how coverage changed

File	Statements	Missing	Coverage	Coverage (new stmts)	Lines missing
data_safe_haven/commands
config.py
data_safe_haven/serialisers
yaml_serialisable_model.py
Project Total

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