Extract capybara config and improve headless_chrome driver config (#28681)

spec/rails_helper.rb

@@ -108,8 +108,6 @@ RSpec.configure do |config|
   end
 
   config.around :each, type: :system do |example|
-    driven_by :selenium, using: :headless_chrome, screen_size: [1600, 1200]
-
     # The streaming server needs access to the database
     # but with use_transactional_tests every transaction
     # is rolled-back, so the streaming server never sees the data