don't use WebKit with Capybara

spec/rails_helper.rb

@@ -20,8 +20,6 @@ Dir[Rails.root.join("spec/support/**/*.rb")].each { |f| require f }
 # If you are not using ActiveRecord, you can remove this line.
 ActiveRecord::Migration.maintain_test_schema!
 
-Capybara.javascript_driver = :webkit
-
 RSpec.configure do |config|
   config.around(:each) do |example|
     Timeout::timeout(example.metadata[:permitted_execution_time] || MAXIMUM_EXECUTION_TIME) { example.run }