Fix suggested use of prelude-user-init-file

to something that will actually work correctly.

core/prelude-custom.el

@@ -71,7 +71,7 @@ Prelude recommends you only put personal customizations in the
 personal folder.  This variable allows you to specify a specific
 folder as the one that should be visited when running
 `prelude-find-user-init-file'.  This can be easily set to the desired buffer
-in lisp by putting `(setq prelude-user-init-file buffer-file-name)'
+in lisp by putting `(setq prelude-user-init-file load-file-name)'
 in the desired elisp file."
   :type 'string
   :group 'prelude)