Remove some Ruby file associations

Those were added upstream to ruby-mode.

modules/prelude-ruby.el

@@ -36,26 +36,6 @@
 
 (prelude-require-packages '(inf-ruby yari))
 
-;; Rake files are ruby, too, as are gemspecs, rackup files, and gemfiles.
-(add-to-list 'auto-mode-alist '("\\.rake\\'" . ruby-mode))
-(add-to-list 'auto-mode-alist '("Rakefile\\'" . ruby-mode))
-(add-to-list 'auto-mode-alist '("\\.gemspec\\'" . ruby-mode))
-(add-to-list 'auto-mode-alist '("\\.ru\\'" . ruby-mode))
-(add-to-list 'auto-mode-alist '("Gemfile\\'" . ruby-mode))
-(add-to-list 'auto-mode-alist '("Guardfile\\'" . ruby-mode))
-(add-to-list 'auto-mode-alist '("Capfile\\'" . ruby-mode))
-(add-to-list 'auto-mode-alist '("\\.cap\\'" . ruby-mode))
-(add-to-list 'auto-mode-alist '("\\.thor\\'" . ruby-mode))
-(add-to-list 'auto-mode-alist '("\\.rabl\\'" . ruby-mode))
-(add-to-list 'auto-mode-alist '("Thorfile\\'" . ruby-mode))
-(add-to-list 'auto-mode-alist '("Vagrantfile\\'" . ruby-mode))
-(add-to-list 'auto-mode-alist '("\\.jbuilder\\'" . ruby-mode))
-(add-to-list 'auto-mode-alist '("Podfile\\'" . ruby-mode))
-(add-to-list 'auto-mode-alist '("\\.podspec\\'" . ruby-mode))
-(add-to-list 'auto-mode-alist '("Puppetfile\\'" . ruby-mode))
-(add-to-list 'auto-mode-alist '("Berksfile\\'" . ruby-mode))
-(add-to-list 'auto-mode-alist '("Appraisals\\'" . ruby-mode))
-
 ;; We never want to edit Rubinius bytecode
 (add-to-list 'completion-ignored-extensions ".rbc")