Fix compiler warning.

* lisp/ob-lilypond.el: Fix compiler warning.

lisp/ob-lilypond.el

@@ -30,10 +30,9 @@
 (require 'ob)
 (require 'ob-eval)
 (require 'ob-tangle)
+(require 'outline)
 (defalias 'lilypond-mode 'LilyPond-mode)
 
-(declare-function show-all "outline" ())
-
 (add-to-list 'org-babel-tangle-lang-exts '("LilyPond" . "ly"))
 
 (defvar org-babel-default-header-args:lilypond '()