Remove `group_analytics_dashboard_dynamic_vsd` feature flag

After we default enabled the group_analytics_dashboard_dynamic_vsd feature flag we should ensure we cleanup / remove the feature flag and related code.

We should now make sure we:

• Remove the feature flag + Update related tests to remove their relevant test cases
• Remove old code
• Remove references to the feature flag in docs
• Remove legacy schema docs

This will also be a good opportunity to revisit our documentation now that we have removed all the legacy configuration information.mo