After all JUnit conversions tracked in JDK-8339170, all tests will be migrated to JUnit 5. We can therefore remove the JUnit Vintage Engine with JUnit 4.

This removes all dependencies to JUnit 4, so Contributors can not accidently mix JUnit 4 and JUnit 5 anymore, which makes JDK-8296284 more easy to solve and simplifies the maintenance done by our side.