{AKS}: Fix the issue that the value passed by option --os-sku in command az aks nodepool update is not processed

[FumingZhang]

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This checklist is used to make sure that common guidelines for a pull request are followed.

{AKS}: Fix the issue that the value passed by option --os-sku in command az aks nodepool update is not processed.
Bug fix for PR #6944.

Related command

az aks nodepool update

General Guidelines

• Have you run azdev style <YOUR_EXT> locally? (pip install azdev required)
• Have you run python scripts/ci/test_index.py -q locally? (pip install wheel==0.30.0 required)

For new extensions:

• My extension description/summary conforms to the Extension Summary Guidelines.

About Extension Publish

There is a pipeline to automatically build, upload and publish extension wheels.
Once your pull request is merged into main branch, a new pull request will be created to update src/index.json automatically.
You only need to update the version information in file setup.py and historical information in file HISTORY.rst in your PR but do not modify src/index.json.

[azure-client-tools-bot-prd]

️✔️Azure CLI Extensions Breaking Change Test

️✔️Non Breaking Changes

[azure-client-tools-bot-prd]

Hi @FumingZhang,
Since the current milestone time is less than 7 days, this pr will be reviewed in the next milestone.

[yonzhan]

AKS

[FumingZhang]

Queued live test (case test_aks_update_agentpool_os_sku) to verify the change. Test passed.

[azclibot]

[Release] Update index.json for extension [ aks-preview ] : https://dev.azure.com/azclitools/internal/_build/results?buildId=105186&view=results