Slim down JAR

[basil]

#455 inadvertently packaged two new JARs into the JPI: spring-core-6.1.14.jar and findbugs-annotations-3.0.1.jar. FindBugs is a static analysis tool without runtime impact, and the Spring Core JAR isn't used at runtime from the plugin, anyway: it is provided by Jenkins core, which takes precedence (see here for details). Nor is shipping spring-core-6.1.14.jar a problem today, as it is not vulnerable to any CVEs that might trip up scanners. But in the long term, it is a liability to ship a Spring library that we do not use that might trip scanners, so slim down the JPI so that it ships the same set of JARs (but with upgraded versions) as we shipped prior to #455.

Testing done

• CI build
• Verified that the JPI contained no new JARs (just upgraded JARs) relative to Upgrade to pac4j 6.x and migrate to EE 9 #455

Submitter checklist

• Make sure you are opening from a topic/feature/bugfix branch (right side) and not your main 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

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 72.19%. Comparing base (41f98d9) to head (12952a3).
Report is 4 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff              @@
##             master     #505      +/-   ##
============================================
+ Coverage     71.73%   72.19%   +0.45%     
- Complexity      222      224       +2     
============================================
  Files            17       17              
  Lines          1033     1050      +17     
  Branches        148      148              
============================================
+ Hits            741      758      +17     
  Misses          201      201              
  Partials         91       91              

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