[AKS]: az aks update: Fix: preview naming of mariner v2

[alexeldeib]

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

For new extensions:

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

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The precondition is to put your code inside this repository and upgrade the version in the pull request but do not modify src/index.json.

[alexeldeib]

we had a last minute naming change here -_-

[yonzhan]

AKS

[FumingZhang]

LGTM