Retire ms.service: "cdn"

[v-alje]

This is a bulk update to change ms.service: "cdn" to ms.service: "azure-cdn" per ceapex Allow List request: 572710

[opbld34]

Docs Build status updates of commit 3683608:

✅ Validation status: passed

File	Status	Preview URL	Details
docfx.json	✅Succeeded

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