org.el: tiny typo in docstring.

lisp/org.el

@@ -11823,7 +11823,7 @@ nil."
 
 (defun org-add-planning-info (what &optional time &rest remove)
   "Insert new timestamp with keyword in the line directly after the headline.
-WHAT indicates what kind of time stamp to add.  TIME indicated the time to use.
+WHAT indicates what kind of time stamp to add.  TIME indicates the time to use.
 If non is given, the user is prompted for a date.
 REMOVE indicates what kind of entries to remove.  An old WHAT entry will also
 be removed."