Remove group option as Rails 4 removed assets group
Remove group option as Rails 4 removed assets group

NHSChoices/activeadmin-sortable-tree,zorab47/active_admin-sortable_tree,zorab47/activeadmin-sortable-tree,zorab47/active_admin-sortable_tree,hotvulcan/activeadmin-sortable-tree,zorab47/active_admin-sortable_tree,zorab47/activeadmin-sortable-tree,zorab47/activeadmin-sortable-tree,tripledub/activeadmin-sortable-tree,wvengen/activeadmin-sortable-tree,hotvulcan/activeadmin-sortable-tree,hotvulcan/activeadmin-sortable-tree