Load `chromedriver-helper.rb`

The bin shim provides by `chromedriver-helper` gem has renamed to
`chromedriver-helper` since 2.0.
https://github.com/flavorjones/chromedriver-helper/pull/58

Since bin of new name is set to driver path in
`lib/chromedriver-helper.rb`, need to load it.

ci/qunit-selenium-runner.rb

@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 require "qunit/selenium/test_runner"
-require "chromedriver/helper"
+require "chromedriver-helper"
 
 driver_options = Selenium::WebDriver::Chrome::Options.new
 driver_options.add_argument("--headless")