Increase capybara default timeout to reduce test flakiness (#34859)

spec/support/capybara.rb

@@ -30,6 +30,10 @@ end
 
 Capybara.javascript_driver = :headless_chrome
 
+# Some of the flaky tests seem to be caused by github runners being too slow for the
+# default timeout of 2 seconds
+Capybara.default_max_wait_time = 8
+
 RSpec.configure do |config|
   config.before(:each, type: :system) do
     driven_by :rack_test