Use system specs instead of feature specs

We get rid of database cleaner, and JavaScript tests are faster because
between tests we now rollback transactions instead of truncating the
database.

spec/rails_helper.rb

@@ -26,10 +26,6 @@ RSpec.configure do |config|
   end
 end
 
-Capybara.register_driver :chrome do |app|
-  Capybara::Selenium::Driver.new(app, browser: :chrome)
-end
-
 Capybara.register_driver :headless_chrome do |app|
   capabilities = Selenium::WebDriver::Remote::Capabilities.chrome(
     "goog:chromeOptions" => {
@@ -44,8 +40,6 @@ Capybara.register_driver :headless_chrome do |app|
   )
 end
 
-Capybara.javascript_driver = :headless_chrome
-
 Capybara.exact = true
 
 OmniAuth.config.test_mode = true