Enable feature flag by default

ee/config/feature_flags/development/performance_roadmap.yml

 ---
 name: performance_roadmap
 introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/65652
-rollout_issue_url:
+rollout_issue_url: https://gitlab.com/gitlab-org/gitlab/-/issues/337198
 milestone: '14.2'
 type: development
 group: group::product planning
-default_enabled: false
+default_enabled: true