update banners to use new css classes

[mawinter69]

See jenkinsci/jenkins#9254

Requires an update once above is merged to reflect the actual Jenkins version that allows using the new css classes

Testing done

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