Add attributions to PA scatterplot flag definition

This adds MR, issue, milestone and group details to the definition for
the productivity_analytics_scatterplot_enabled feature flag.

ee/config/feature_flags/development/productivity_analytics_scatterplot_enabled.yml

 ---
 name: productivity_analytics_scatterplot_enabled
-introduced_by_url: 
-rollout_issue_url: 
-milestone: 
+introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/17735
+rollout_issue_url: https://gitlab.com/gitlab-org/gitlab/-/issues/13412
+milestone: '12.4'
 type: development
-group: 
+group: group::optimize
 default_enabled: true