ob-lilypond: Resolve FIXME

* lisp/ob-lilypond.el: Use `org-src-lang-modes' to inform Org babel
about non-standard mode name instead of using `defalias'.
* testing/lisp/test-ob-lilypond.el (ob-lilypond/check-lilypond-alias):
Remove test.

lisp/ob-lilypond.el

@@ -40,10 +40,8 @@
 
 (declare-function org-fold-show-all "org-fold" (&optional types))
 
-;; FIXME: Doesn't this rather belong in lilypond-mode.el?
-(defalias 'lilypond-mode 'LilyPond-mode)
-
 (add-to-list 'org-babel-tangle-lang-exts '("LilyPond" . "ly"))
+(add-to-list 'org-src-lang-modes '("lilypond" . "LilyPond"))
 
 (defvar org-babel-default-header-args:lilypond '()
   "Default header arguments for lilypond code blocks.

testing/lisp/test-ob-lilypond.el

@@ -32,9 +32,6 @@
 (ert-deftest ob-lilypond/feature-provision ()
   (should (featurep 'ob-lilypond)))
 
-(ert-deftest ob-lilypond/check-lilypond-alias ()
-  (should (fboundp 'lilypond-mode)))
-
 (ert-deftest ob-lilypond/org-babel-tangle-lang-exts ()
   (let ((found nil)
         (list org-babel-tangle-lang-exts))