[org] replace org-bullets with org-superstar

org-bullets has been deprecated

layers/+emacs/org/README.org

@@ -63,7 +63,7 @@ This layer enables [[http://orgmode.org/][org mode]] for Spacemacs.
 
 ** Features:
 - Vim inspired key bindings are provided by [[https://github.com/Somelauw/evil-org-mode][evil-org-mode]]
-- Nicer bullet via [[https://github.com/sabof/org-bullets][org-bullets]]
+- Nicer bullet via [[https://github.com/integral-dw/org-superstar-mode][org-superstar-mode]]
 - A [[https://cirillocompany.de/pages/pomodoro-technique][pomodoro method]] integration via [[https://github.com/lolownia/org-pomodoro][org-pomodoro]]
 - Presentation mode via [[https://github.com/rlister/org-present][org-present]]
 - Insertion of images via [[https://github.com/abo-abo/org-download][org-download]]
@@ -254,16 +254,16 @@ To install Trello support set the variable =org-enable-trello-support= to =t=.
 ** Different bullets
 You can tweak the bullets displayed in the org buffer in the function
 =dotspacemacs/user-config= of your dotfile by setting the variable
-=org-bullets-bullet-list=. By default the list is set to =("◉" "○" "✸" "✿")=.
+=org-superstar-headline-bullets-list=. By default the list is set to =("◉" "○" "✸" "✿")=.
 
 #+BEGIN_SRC emacs-lisp
-  (setq org-bullets-bullet-list '("■" "◆" "▲" "▶"))
+  (setq org-superstar-bullet-list '("■" "◆" "▲" "▶"))
 #+END_SRC
 
-You can disable the fancy bullets entirely by adding =org-bullets= to =dotspacemacs-excluded-packages=.
+You can disable the fancy bullets entirely by adding =org-superstar= to =dotspacemacs-excluded-packages=.
 
 #+BEGIN_SRC emacs-lisp
-  (dotspacemacs-excluded-packages '(org-bullets))
+  (dotspacemacs-excluded-packages '(org-superstar))
 #+END_SRC
 
 ** Project support

layers/+spacemacs/spacemacs-org/packages.el

@@ -22,7 +22,7 @@
     ;; `org' package.
     (default-org-config :location built-in)
     (org-plus-contrib :step pre)
-    org-bullets
+    org-superstar
     (space-doc :location local)
     toc-org
     ))
@@ -62,10 +62,10 @@
       ;; Open links and files with RET in normal state
       (evil-define-key 'normal org-mode-map (kbd "RET") 'org-open-at-point)))))
 
-(defun spacemacs-org/init-org-bullets ()
-  (use-package org-bullets
+(defun spacemacs-org/init-org-superstar ()
+  (use-package org-super-star
     :defer t
-    :init (add-hook 'org-mode-hook 'org-bullets-mode)))
+    :init (add-hook 'org-mode-hook 'org-superstar-mode)))
 
 (defun spacemacs-org/init-toc-org ()
   (use-package toc-org