Add group::editor feature flag info

config/feature_flags/development/build_service_proxy.yml

 ---
 name: build_service_proxy
-introduced_by_url: 
-rollout_issue_url: 
-group: 
+introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/9723
+rollout_issue_url:
+group: group::editor
 type: development
 default_enabled: false

config/feature_flags/development/snippet_multiple_files.yml

 ---
 name: snippet_multiple_files
-introduced_by_url: 
-rollout_issue_url: 
-group: 
+introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/32416
+rollout_issue_url: https://gitlab.com/gitlab-org/gitlab/-/issues/217809
+group: group::editor
 type: development
 default_enabled: false