Update gitlab-api dependency

[zbynek]

Downstream of jenkinsci/gitlab-api-plugin#121 -- changes some inports to fit the new API.

See also https://issues.jenkins.io/browse/JENKINS-76091

Testing done

Checked that together with the upstream PR and a hack to add jersey3-api dependency to that plugin this resolves the issue of authentication not working with Jackson plugin v 2.20.0.

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
• [n/a] Ensure you have provided tests that demonstrate the feature works or the issue is fixed

[MarkEWaite]

Due to the breaking changes in the transition from GitLab API 5.8.x to GitLab API 6.x, we need to plan a coordinated release of this pull request and other pull requests:

• Update gitlab4j to 6.1.0, update Jenkins BOM, require Jenkins 2.504.3 gitlab-api-plugin#121
• Migrate gitlab api from 5 to 6 gitlab-branch-source-plugin#511
• Use GitLab API plugin 6.1.0 gitlab-logo-plugin#131

If a user installs the new release of GitLab API plugin that includes GitLab API 6.x, without updating any of the other installed plugins, those installed plugins will likely be broken and report errors.

I will be out of the office from Oct 27 - Nov 7, so won't be able to help coordinate the release of those plugins until after I return. Maintainers of those plugins need to all agree that they will release a new version soon after the release of this pull request.