fix: reuse Capybara chrome instance for lighthouse audits (#616)

Right now we actually spin up a whole new instance of Chrome when
running lighthouse tests which besides being costly also means that none
of our presetup work such as logging users in happens 😬

Author: G-Rath

variants/accessibility/spec/rails_helper.rb

@@ -5,11 +5,13 @@
   REQUIRE
 end
 
-insert_into_file! "spec/rails_helper.rb", after: /# Add other Chrome arguments here\n/ do
+insert_into_file! "spec/rails_helper.rb", before: /# Add other Chrome arguments here\n/ do
   <<~OPTIONS
-    # Lighthouse Matcher options
+    # have lighthouse use the instance of Chrome launched by Capybara, rather than
+    # starting its own instance - this is important as otherwise setup work such
+    # signing in as a user to access authenticated pages won't work properly
     options.add_argument("--remote-debugging-port=9222")
-    Lighthouse::Matchers.chrome_flags = %w[headless=new no-sandbox]
+    Lighthouse::Matchers.remote_debugging_port = 9222
     Lighthouse::Matchers.results_directory = Rails.root.join("tmp/lighthouse")
   OPTIONS
 end