Group information to group ndjson feature flags

config/feature_flags/development/group_export_ndjson.yml

 ---
 name: group_export_ndjson
-introduced_by_url: 
-rollout_issue_url: 
-group: 
+introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/29590
+rollout_issue_url:
+group: import
 type: development
 default_enabled: true

config/feature_flags/development/group_import_ndjson.yml

 ---
 name: group_import_ndjson
-introduced_by_url: 
-rollout_issue_url: 
-group: 
+introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/29716
+rollout_issue_url:
+group: import
 type: development
 default_enabled: true