v21.0.0

Breaking changes

This support Gradle 9.x by upgrading to codenarc 3.6.0-groovy-4.0 and Groovy 4.0.

This is not backwards compatible

What's Changed

• com.google.guava:guava 33.4.8-jre by @candrews in #427
• Update com.netflix.nebula.plugin plugin to use sonatype central portal by @OdysseusLives in #431
• Migrate to Gradle 9.x by @rpalcolea in #432

Full Changelog: v20.6.2...v21.0.0