[JENKINS 74095] Remove legacy inline onClick handler in AbstractPlotPublisher/config.jelly

[shlomomdahan]

Jira:

• JENKINS-74095

What has been done

1. Remove the legacy onClick handler in AbstractPlotPublisher/config.jelly as part of effort to improve CSP compatibility.

Before Changes
After Changes

How to test

1. Create a freestyle project
2. In post build steps, select: Plot build data
3. Add the data series file and check validation triggers.
   

Checklist

• Git commits follow best practices
• Build passes in Jenkins
• Appropriate tests or explanation to why this change has no tests
• Pull Request is marked with appropriate label (see .github/release-drafter.yml)
• JIRA issue is well described (problem explanation, steps to reproduce, screenshots)
• For dependency updates: links to external changelogs and, if possible, full diffs