Fix issue with output for Get-AzAks

[cormacpayne]

Description

Fix for issue #9847

Checklist

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• The title of the PR is clear and informative
• The appropriate ChangeLog.md file(s) has been updated:
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• The PR does not introduce breaking changes
• If applicable, the changes made in the PR have proper test coverage
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  • a cmdlet design review was approved for the changes in this repository (Microsoft internal only)
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