Deprecated Branch Alert - Actual Branch IS the Most Recent Version

The alert you are receiving is about the retirement of the platform branch itself. This means that ElasticBeanstalk will not be introducing any new platform versions/updates for that branch. That's why the recommended newest branch is the exact same branch you are running, because no new version has been released.

When a component of a supported platform branch is marked End of Life (EOL) by its supplier, Elastic Beanstalk marks the platform branch as retired. Components of a platform branch include the following: operating system (OS), runtime language version, application server, or web server.

Once a platform branch is marked as retired, Elastic Beanstalk stops providing maintenance updates, including security updates. You can refer to the Elastic Beanstalk platform support policy for more details.

Unfortunately, you cannot clear the "deprecated" status. What you can do, is migrating your environment to a supported platfrom branch using a Blue/Green deployment.