Enable VSD count aggregation setting

What does this MR do and why?

This change enables the Value Stream Dashboard aggregation collection setting on the top-level group setting page. The data collection was already tested with the gitlab-org group and it's working as expected.

• Rollout issue: #411223 (closed)
• Docs MR: !127118 (merged)

MR acceptance checklist

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Related to #411223 (closed)