Fix #derived_versions and #active_sibling_versions returning an Array… #518

Job	Run time
RuboCop	26s
RSpec and Cucumber (2.7, gemfiles/rails-7-0.gemfile, false)	1m 25s
RSpec and Cucumber (3.0, gemfiles/rails-7-0.gemfile, false)	1m 1s
RSpec and Cucumber (3.1, gemfiles/rails-7-0.gemfile, false)	1m 8s
RSpec and Cucumber (3.2, gemfiles/rails-7-0.gemfile, false)	1m 8s
RSpec and Cucumber (jruby, gemfiles/rails-7-0.gemfile, false)	2m 26s
RSpec and Cucumber (2.5, gemfiles/rails-6-0.gemfile, false)	1m 14s
RSpec and Cucumber (2.6, gemfiles/rails-6-1.gemfile, false)	1m 50s
RSpec and Cucumber (3.2, gemfiles/rails-7-1.gemfile, false)	1m 27s
RSpec and Cucumber (3.2, gemfiles/rails-main.gemfile, true)	1m 7s
RSpec and Cucumber (ruby-head, gemfiles/rails-7-1.gemfile, false)	1m 14s
RSpec and Cucumber (jruby-head, gemfiles/rails-7-0.gemfile, true)	2m 32s
	16m 58s

Provide feedback