org-list.el (org-sort-list): Fix typo in prompt string

* lisp/org-list.el (org-sort-list): Fix typo in prompt string.

lisp/org-list.el

@@ -2898,7 +2898,7 @@ function is being called interactively."
 	    (or compare-func
 		(and interactive?
 		     (org-read-function
-		      (concat "Function for comparing keys"
+		      (concat "Function for comparing keys "
 			      "(empty for default `sort-subr' predicate): ")
 		      'allow-empty))))
 	   ((= dcst ?t) #'<)