These blocks are added by the customize interface, as Noufal pointed out. You can move them to a separate file, though, if you like.
Just add this to your ~/.emacs.d/init.el:
(setq custom-file "~/.emacs.d/custom.el")
(load custom-file)
or, if you’re still using an old-fashioned ~/.emacs file:
(setq custom-file "~/.custom.el")
(load custom-file)
A slightly more complex snippet that will work in either case is:
(setq custom-file (expand-file-name "custom.el" user-emacs-directory))
(load custom-file)