[Routing Preference] : Updated the Flatten property and added example . Linked to PR#7689

[HimanshuChhabra]

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[azuresdkci]

Can one of the admins verify this patch?

[HimanshuChhabra]

This PR is linked to: #7689

[AutorestCI]

Automation for azure-sdk-for-python

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Azure/azure-sdk-for-python#8379

[AutorestCI]

Automation for azure-sdk-for-go

The initial PR has been merged into your service PR:
Azure/azure-sdk-for-go#6264