Add missing downtime v2 defaults

[api-clients-generation-pipeline[bot]]

See DataDog/datadog-api-spec#2310 Test branch datadog-api-spec/test/carl/add-downtime-v2-defaults

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This issue has been automatically marked as stale because it has not had activity in the last 30 days. Note that the issue will not be automatically closed, but this notification will remind us to investigate why there's been inactivity.

[github-actions[bot]]

This PR has been automatically marked as stale because it has not had activity in the last 30 days. If there is no activity for another 90 days, this issue will be automatically closed.