Delete :depends / Add :after

Hello Dimitri:
Accroding to emacswiki, cedet is part of the standard Emacs distribution since version 23.2., so I think that matlab-mode doesn't need to depend on cedet(-bzr) anymore. By the way, users should add (require 'cedet) if cedet or semantic is needed.
I have test this new recipe with Emacs 24.3, it works fine.