After #27351 the journald input is available in filebeat, so we no longer need journalbeat.

• Remove journalbeat from the packaging. https://github.com/elastic/infra/pull/32395
• Remove the code Remove Journalbeat #29131
• Remove other references. https://github.com/elastic/infra/issues/33342

Changes in documentation will be taken care of in https://github.com/elastic/observability-docs/issues/1173

NOTE: This cannot be implemented until journalbeat has been removed from the release manager and the CI pipeline.