Gemfile in asciidoctor-epub3-2.0.1 vs Gemfile in asciidoctor-epub3-2.1.0

@@ -7,10 +7,6 @@
 
 group :optional do
   # epubcheck-ruby might be safe to be converted into runtime dependency,
   # but could have issues when packaged into asciidoctorj-epub3
   gem 'epubcheck-ruby', '~> 5.1.0.0'
-
-  # Kindlegen is unavailable neither for 64-bit x86 macOS nor for ARM
-  # Also, skip JRuby on Windows for now. See https://github.com/jruby/jruby/issues/7171
-  gem 'kindlegen', '~> 3.1.0' unless RUBY_PLATFORM =~ /darwin/ || (Gem.win_platform? && RUBY_ENGINE == 'jruby')
 end