org-element: Fix typo in docstring

* lisp/org-element.el (org-element-text-markup-successor): Fix typo in
  docstring.

lisp/org-element.el

@@ -2210,8 +2210,6 @@ CONTENTS is the contents of the object."
 
 LIMIT bounds the search.
 
-LIMIT bounds the search.
-
 Return value is a cons cell whose CAR is a symbol among `bold',
 `italic', `underline', `strike-through', `code' and `verbatim'
 and CDR is beginning position."