babel: mscgen: Delete unnecessary language-specific expansion function

    * ob-mscgen.el (org-babel-expand-body:mscgen): Delete
    function (automatically handled by generic version)

lisp/ob-mscgen.el

@@ -62,9 +62,6 @@
   '((:results . "file") (:exports . "results"))
   "Default arguments to use when evaluating a mscgen source block.")
 
-(defun org-babel-expand-body:mscgen (body params)
-  "Expand BODY according to PARAMS, return the expanded body." body)
-
 (defun org-babel-execute:mscgen (body params)
   "Execute a block of Mscgen code with Babel.
 This function is called by `org-babel-execute-src-block'.