Update epubcheck-ruby requirement from ~> 4.2.2.0 to ~> 4.2.4.0 (#341)
Update epubcheck-ruby requirement from ~> 4.2.2.0 to ~> 4.2.4.0 (#341)

Updates the requirements on [epubcheck-ruby](https://github.com/takahashim/epubcheck-ruby) to permit the latest version.
- [Release notes](https://github.com/takahashim/epubcheck-ruby/releases)
- [Commits](https://github.com/takahashim/epubcheck-ruby/compare/v4.2.2.0...v4.2.4.0)

Signed-off-by: dependabot-preview[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@dependabot.com>

Co-authored-by: dependabot-preview[bot] <6a4c1c4838f800d1998274cd5234e1f65c55e90c@users.noreply.github.com>
asciidoctor/asciidoctor-epub3