[JENKINS-65237] bump groovy to 2.4.21

[car-roll]

Attempt upgrade to latest groovy 2.4 release

• [ ] Make sure you are opening from a topic/feature/bugfix branch (right side) and not your master branch!
• [ ] Ensure that the pull request title represents the desired changelog entry
• [ ] Please describe what you did
• [ ] Link to relevant issues in GitHub or Jira
• [ ] Link to relevant pull requests, esp. upstream and downstream changes
• [ ] Ensure you have provided tests - that demonstrates feature works or fixes the issue

[car-roll]

closing in favor of #73