PearPackagingMavenPlugin has ancient JUnit dependency

The PearPackagingMavenPlugin has a dependency on org.apache.maven:maven-project which is ancient and which has a transitive compile dependency on junit 3.8.1! This is causing trouble downstream when projects try to switch to JUnit 5.

Instead, it should depend on org.apache.maven:maven-core which is the current provider of the MavenProject class.