Pulumi: Fix selectors not updating

[JimMadge]

✅ Checklist

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⤴️ Summary

• Update Nexus allowlist container image to a version with a fallback method to trigger updating allowlists
• Add environment variables to container instance to use fallback method

🌂 Related issues

Related to alan-turing-institute/nexus-allowlist#27

🔬 Tests

[JimMadge]

@craddm 👈

[craddm]

LGTM