Don't consider play-sound-file to be a 'safe' function (bug#44018)

While there are currently no known security holes in play-sound-file,
the attack surface is considerable and historically audio file
processing has had more than its share of security problems; the
benefit to risk ratio is low.

* lisp/emacs-lisp/unsafep.el: Don't mark play-sound-file as safe.

lisp/emacs-lisp/unsafep.el

@@ -101,7 +101,7 @@ in the parse.")
 	     ;;Macros from subr.el
 	     save-match-data unless when
 	     ;;Functions from subr.el that have side effects
-	     split-string replace-regexp-in-string play-sound-file))
+	     split-string replace-regexp-in-string))
   (put x 'safe-function t))
 
 ;;;###autoload