Update policy definition 'Deny-Subnet-Without-Udr' to include default value 'RouteServerSubnet' in parameter 'excludedSubnets'

[wesley32]

Overview/Summary

This PR fixes/adds/changes/removes

1. Add default value 'RouteServerSubnet' to parameter 'excludedSubnets' in policy definition 'Deny-Subnet-Without-Udr',

Breaking Changes

1. None

Testing Evidence

1. Small change to default values:

As part of this Pull Request I have

• [X ] Checked for duplicate Pull Requests
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• Ensured my code/branch is up-to-date with the latest changes in the main branch
• Performed testing and provided evidence.
• Ensured contribution guidance is followed.
• Updated relevant and associated documentation.
• Updated the "What's New?" wiki page (located: /docs/wiki/whats-new.md)

[wesley32]

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[jtracey93]

superseded by #2128