Fix/gh actions windows spec failure

[skoji]

No description provided.

[slonopotamus]

I suspect, some of gepub changes cause this issue. I think that gepub stopped properly closing file descriptor, that's why deletion fails on Windows.

I'm also observing this in asciidoctor-epub3 test suite: https://github.com/asciidoctor/asciidoctor-epub3/actions/runs/9051436682/job/24867956933#step:5:488

  32) Asciidoctor::Epub3::Converter - Xref resolves xref to inline anchor
      Failure/Error: output.generate_epub target

      Errno::EACCES:
        Permission denied - D:/a/asciidoctor-epub3/asciidoctor-epub3/spec/temp/book.epub
      # ./vendor/bundle/jruby/3.1.0/gems/gepub-1.0.16/lib/gepub/book.rb:233:in `generate_epub'
      # ./lib/asciidoctor-epub3/converter.rb:19:in `write'
      # ./vendor/bundle/jruby/3.1.0/gems/asciidoctor-2.0.22/lib/asciidoctor/document.rb:989:in `write'
      # ./vendor/bundle/jruby/3.1.0/gems/asciidoctor-2.0.22/lib/asciidoctor/convert.rb:124:in `convert'
      # ./vendor/bundle/jruby/3.1.0/gems/asciidoctor-2.0.22/lib/asciidoctor/convert.rb:190:in `block in convert_file'
      # ./vendor/bundle/jruby/3.1.0/gems/asciidoctor-2.0.22/lib/asciidoctor/convert.rb:190:in `convert_file'
      # ./spec/spec_helper.rb:72:in `convert'
      # ./spec/spec_helper.rb:79:in `to_epub'
      # ./spec/xref_spec.rb:30:in `block in <main>'

Note that gepub 1.0.15 passes without issues: https://github.com/slonopotamus/asciidoctor-epub3/actions/runs/9051508194/job/24868104673

As a workaround, I currently locked gepub to 1.0.15 in asciidoctor-epub3: asciidoctor/asciidoctor-epub3#474

[slonopotamus]

Created #141 for this issue.