Remove `--builder` option from `rails` command

Ability to use a custom builder by passing `--builder` (or `-b`) has
been removed. Consider using application template instead. See this
guide for more detail:
http://guides.rubyonrails.org/rails_application_templates.html
Merge pull request #9401 from sikachu/master-remove-builder-option

Remove `--builder` option from `rails` command