Update the clone of `hudson.Extension` in this plugin to the latest in Jenkins core

[steven-terrana]

fixes #199 by updating the minimal clone of hudson.Extension present in this plugin.

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• [x] Ensure that the pull request title represents the desired changelog entry
• [x] Please describe what you did
• [x] Link to relevant issues in GitHub or Jira
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• [ ] Ensure you have provided tests - that demonstrates feature works or fixes the issue

[sghill]

This was released as v0.44.0