[JENKINS-73788] Reduce metrics bloat relating to provisioning requests

[PayBas]

See https://issues.jenkins.io/browse/JENKINS-73788 for details

Testing done

Compiled+unittested the plugin.
Installed to local Jenkins without issues.
Small scale test indicates that the troublesome metrics are no longer collected. I can roll this out to a larger Jenkins instance for more thorough (live) testing, but that will have to wait for our maintenance window.

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

[Vlatombe]

Follows up #872

[Vlatombe]

This looks good. I don't have on-hands experience with using these metrics in real production environments, but given its location, I can understand it can be problematic, so I'm good with removing it.

[Vlatombe]

Thank you for your contribution!