Enable the vsa_incremental_worker FF by default

This change enables the incremental data collection for the aggregated
Value Stream Analytics feature. We release the data collection part
earlier than 15.0 in order to ensure that we will have aggregated data
when the feature if fully released.

Changelog: added

config/feature_flags/development/vsa_incremental_worker.yml

@@ -5,4 +5,4 @@ rollout_issue_url: https://gitlab.com/gitlab-org/gitlab/-/issues/353453
 milestone: '14.9'
 type: development
 group: group::optimize
-default_enabled: false
+default_enabled: true