Update example command to use correct variable name

[Keboo]

Under the Run a sample application header. The Note suggest using the command echo $IDENTITY_NAME, however the variable created and used i the rest of the doc is $POD_IDENTITY_NAME. Suggest updating the example command to be echo $POD_IDENTITY_NAME.
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Document Details

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• ID: c3c187c0-27f1-11c9-41af-6c65ca36e77e
• Version Independent ID: 249a570b-90ba-4a11-4467-320f0369ec25
• Content: Use Azure Active Directory pod-managed identities in Azure Kubernetes Service (Preview) - Azure Kubernetes Service
• Content Source: articles/aks/use-azure-ad-pod-identity.md
• Service: container-service
• GitHub Login: @zr-msft
• Microsoft Alias: zarhoads

[kobulloc-MSFT]

@Keboo Thank you for bringing this to our attention! We are reviewing the documentation and will get back to you shortly.

[kobulloc-MSFT]

@Keboo A PR has been made to address this and you should see the changes go live shortly. Thank you for helping to improve the documentation!