Update azure-arc-create-container-app.md

[zaidmohd]

Fixed "az containerapp" command. Fixed image name "mcr.microsoft.com/azuredocs/containerapps-helloworld:latest"

[prmerger-automator[bot]]

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[opbld31]

Learn Build status updates of commit b686af6:

:white_check_mark: Validation status: passed

File	Status	Preview URL	Details
articles/container-apps/azure-arc-create-container-app.md	:white_check_mark:Succeeded

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[Jak-MS]

@craigshoemaker

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[craigshoemaker]

Thanks, @zaidmohd!

This fix was published via another PR, so I am going to #please-close this for now.