Support activesupport v7

[masayuki0812]

activesupport 7 has String#{demodulize,underscore} as same as 6. Ref: gongo#102

• 7.0.6

  • String#demodulize / ActiveSupport::ActiveSupport::demodulize
  • String#underscore / ActiveSupport::ActiveSupport::underscore

• 6.1.7.4

  • String#demodulize / ActiveSupport::ActiveSupport::demodulize
  • String#underscore / ActiveSupport::ActiveSupport::underscore

Travis is not running now, but I confirmed test passed on local. So, it seems ok.

$ bundle exec rake test
/Users/me/.rbenv/versions/3.2.2/bin/ruby -I"lib:test" /Users/me/.rbenv/versions/3.2.2/lib/ruby/gems/3.2.0/gems/rake-13.0.6/lib/rake/rake_test_loader.rb "test/turnip_formatter/renderer/html/test_data_table.rb" "test/turnip_formatter/renderer/html/test_doc_string.rb" "test/turnip_formatter/renderer/html/test_index.rb" "test/turnip_formatter/renderer/html/test_runtime_error.rb" "test/turnip_formatter/renderer/html/test_statistics_feature.rb" "test/turnip_formatter/renderer/html/test_statistics_speed.rb" "test/turnip_formatter/renderer/html/test_statistics_tag.rb" "test/turnip_formatter/renderer/html/test_step.rb" "test/turnip_formatter/renderer/test_html.rb" "test/turnip_formatter/resource/scenario/test_failure.rb" "test/turnip_formatter/resource/scenario/test_pass.rb" "test/turnip_formatter/resource/scenario/test_pending.rb" "test/turnip_formatter/step_template/test_base.rb" "test/turnip_formatter/step_template/test_exception.rb" "test/turnip_formatter/step_template/test_source.rb" 
Loaded suite /Users/me/.rbenv/versions/3.2.2/lib/ruby/gems/3.2.0/gems/rake-13.0.6/lib/rake/rake_test_loader
Started
Finished in 0.127823 seconds.
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51 tests, 70 assertions, 0 failures, 0 errors, 0 pendings, 0 omissions, 0 notifications
100% passed
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398.99 tests/s, 547.63 assertions/s