Remove all mention of WAC as its not supported for windows containers

[ritikaguptams]

WAC team does not support the containers extension for windows containers anymore. Fyi @mattatmsft

[learn-build-service-prod[bot]]

Learn Build status updates of commit 8cc5d7f:

:warning: Validation status: warnings

File	Status	Preview URL	Details
virtualization/windowscontainers/quick-start/set-up-environment.md	:warning:Warning		Details

virtualization/windowscontainers/quick-start/set-up-environment.md

• Line 25, Column 7: [Warning: bookmark-not-found] Cannot find bookmark '#windows-admin-center' in 'quick-start/set-up-environment.md'.
• Line 5, Column 12: [Suggestion: ms-author-invalid - See documentation] Invalid value for 'ms.author', 'brasmith' is not a valid Microsoft alias.

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