--natural-title-bar option was removed from this formula, in order to
duplicate its effect add following line to your init.el file
(add-to-list 'default-frame-alist '(ns-transparent-titlebar . t))
(add-to-list 'default-frame-alist '(ns-appearance . dark))
or:
(add-to-list 'default-frame-alist '(ns-transparent-titlebar . t))
(add-to-list 'default-frame-alist '(ns-appearance . light))