Mark as deprecated

Can you please note on this page (like you do here: https://docs.microsoft.com/en-us/cli/vsts/overview?view=vsts-cli-latest) that this CLI is deprecated?

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#### Document Details

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* ID: 9c63192e-dc64-73c4-8c9d-f3854cf0887b
* Version Independent ID: 7c6632f8-8208-3779-2b6f-cc86bb1bce7d
* Content: [Get started with the VSTS CLI](https://docs.microsoft.com/en-us/cli/vsts/get-started?view=vsts-cli-latest)
* Content Source: [latest/docs-ref-conceptual/get-started.md](https://github.com/MicrosoftDocs/vsts-docs-cli-python/blob/live/latest/docs-ref-conceptual/get-started.md)
* Product: **vsts**
* Technology: **vsts**
* GitHub Login: @elbatk
* Microsoft Alias: **elbatk**