Upgrade network sdk and rerun privatedns tests

[pranavpnair]

Description

Re-Recorded test files after Network SDK upgrade for PrivateDns module.

Email from Anton:
Hi, @pranav Nair,

We’re updating Network SDK in Azure PowerShell which uses a newer API version. Because of that we also have to update PrivateDns’ test recordings but those tests are failing for us with “Long running operation failed with status 'Failed'” (you can find the list in attachments).
Could you please set version of “Microsoft.Azure.Management.Network” in PrivateDns.Test.csproj to “19.9.0-preview” and re-record PrivateDns’ tests (you can either open a PR in master or just send updated JSONs to me)? That would help us get unblocked.

Best regards,
Anton Evseev

Checklist

• I have read the Submitting Changes section of CONTRIBUTING.md
• The title of the PR is clear and informative
• The appropriate change log has been updated
• The PR does not introduce breaking changes
• If applicable, the changes made in the PR have proper test coverage
• For public API changes to cmdlets:
  • the changes have gone through a cmdlet design review (Microsoft internal partners only)
  • the cmdlet markdown files were generated using the platyPS module