Remove useBeta property from pom.xml

[strangelookingnerd]

Now that the permission Jenkins.MANAGE is out of beta (jenkinsci/jenkins#10183) the useBeta property is no longer required.

This is still a draft, since it will take some time until that change is shipped in an LTS and this plugin updates to it.
I would like to use this PR as a reminder and update / merge it once the requirements are met.

Testing done

Validated with mvn clean verify

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

[strangelookingnerd]

There seem to be other uses of Beta - closing this.