Replace deprecated Set-AzDiagnosticSetting

[jemrobinson]

✅ Checklist

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⤴️ Summary

Set-AzDiagnosticSetting is deprecated for Az.Monitor >= 4.2.0. Here we update to the new syntax and update the required module version.

🌂 Related issues

Part of #1169.

🔬 Tests

Tested on a local SHM deployment