set default project and group visibility to public

This change matches existing settings, and is thus a no-op.  Tested
against existing configuration.

settings.yaml

@@ -96,6 +96,11 @@ restricted_visibility_levels:
   - internal
   - private
 
+# Set default project & group visibility to public:
+# Admin area, Settings, Visibility and access controls
+default_project_visibility: "public"
+default_group_visibility: "public"
+
 # List of accepted import sources: Admin Area, Settings, General, Visibility
 # and access controls, Import sources:
 import_sources: