ui test unversioned course and script redirects

[davidsbailey]

attempts to fill in a testing blind spot for the HB errors linked in #42221.

the production regression was tied to script/course caching being enabled. drone does not have script caching enabled, but the test machine does:

code-dot-org/dashboard/app/models/script.rb

Lines 387 to 390 in b8da6aa

	def self.should_cache?
	return false if Rails.application.config.levelbuilder_mode
	return false unless Rails.application.config.cache_classes
	return false if ENV['UNIT_TEST'] || ENV['CI']

Testing story

I ran this cross-browser and with caching enabled here: #42230