Once the core parent POM changes for requiring Java 11 (JENKINS-68569) are merged and release, the next step is to upgrade core and core components to that core parent POM release and remove the Java 8 builds from the Jenkinsfile for any core and any components that are part of the delivered .war (e.g., Remoting, Stapler, etc.).

Core components that are not part of the delivered .war (e.g., maven-hpi-plugin, jenkins-test-harness, etc.) still need to support older versions of Jenkins core, so we should continue building and testing these with both Java 8 and Java 11. These use the regular core parent POM, which we are planning on removing Java 8 support from. I suppose we could inline the relevant Java 8 specific profiles that we are deleting from the core parent POM into these two repositories in order to be able to upgrade them to the latest core parent POM while still supporting Java 8. I will deal with this when I get to it, but I do not imagine this being a big issue.