Backport commit 5d51403ce from Emacs

; Typo fixes, mostly repeated words
5d51403ceb9b86a1bfa66f00c7af39f1200e65f1
Paul Eggert
Mon Oct 9 22:55:06 2017 -0700

lisp/org-faces.el

@@ -291,7 +291,7 @@ determines if it is a foreground or a background color."
 (defcustom org-priority-faces nil
   "Faces for specific Priorities.
 This is a list of cons cells, with priority character in the car
-and faces in the cdr.  The face can be a symbol, a color as
+and faces in the cdr.  The face can be a symbol, a color
 as a string, or a property list of attributes, like
     (:foreground \"blue\" :weight bold :underline t).
 If it is a color string, the variable `org-faces-easy-properties'