Upgrade asciidoctorj-diagram to 2.2.3

[robertpanzer]

Thank you for opening a pull request and contributing to AsciidoctorJ!

Please take a bit of time giving some details about your pull request:

Kind of change

• [ ] Bug fix
• [x] New non-breaking feature
• [ ] New breaking feature
• [ ] Documentation update
• [ ] Build improvement

Description

What is the goal of this pull request?

Upgrade asciidoctorj-diagram to the latest and greatest version, 2.2.3.