Lift Beta constraint from Jenkins.MANAGE permission

[strangelookingnerd]

This PR removes the @Restricted(Beta.class) annotation from Jenkins.MANAGE.
I'd say that the beta-status is long over, there are plenty of plugins using it without issues.
Once the change is merged, the affected plugins may also get rid of the useBeta property in their pom.xml.

Testing done

Ran mvn clean verify without issue.

Proposed changelog entries

• Lift Beta constraint from Jenkins.MANAGE permission

Proposed upgrade guidelines

N/A

### Submitter checklist
- [x] The Jira issue, if it exists, is well-described.
- [x] The changelog entries and upgrade guidelines are appropriate for the audience affected by the change (users or developers, depending on the change) and are in the imperative mood (see [examples](https://github.com/jenkins-infra/jenkins.io/blob/master/content/_data/changelogs/weekly.yml)). Fill in the **Proposed upgrade guidelines** section only if there are breaking changes or changes that may require extra steps from users during upgrade.
- [x] There is automated testing or an explanation as to why this change has no tests.
- [x] New public classes, fields, and methods are annotated with `@Restricted` or have `@since TODO` Javadocs, as appropriate.
- [x] New deprecations are annotated with `@Deprecated(since = "TODO")` or `@Deprecated(forRemoval = true, since = "TODO")`, if applicable.
- [x] New or substantially changed JavaScript is not defined inline and does not call `eval` to ease future introduction of Content Security Policy (CSP) directives (see [documentation](https://www.jenkins.io/doc/developer/security/csp/)).
- [x] For dependency updates, there are links to external changelogs and, if possible, full differentials.
- [x] For new APIs and extension points, there is a link to at least one consumer.

Desired reviewers

N/A

Before the changes are marked as ready-for-merge:

### Maintainer checklist
- [x] There are at least two (2) approvals for the pull request and no outstanding requests for change.
- [x] Conversations in the pull request are over, or it is explicit that a reviewer is not blocking the change.
- [x] Changelog entries in the pull request title and/or **Proposed changelog entries** are accurate, human-readable, and in the imperative mood.
- [ ] Proper changelog labels are set so that the changelog can be generated automatically.
- [ ] If the change needs additional upgrade steps from users, the `upgrade-guide-needed` label is set and there is a **Proposed upgrade guidelines** section in the pull request title (see [example](https://github.com/jenkinsci/jenkins/pull/4387)).
- [ ] If it would make sense to backport the change to LTS, a Jira issue must exist, be a _Bug_ or _Improvement_, and be labeled as `lts-candidate` to be considered (see [query](https://issues.jenkins.io/issues/?filter=12146)).

[krisstern]

/label ready-for-merge

This PR is now ready for merge, after ~24 hours, we will merge it if there's no negative feedback.

[jglick]

FTR #4909