Java 10 was recently released and support for Java 9 has ended since it's
not a LTS release. I've added a kafka-trunk Jenkins job for Java 10 and
disabled the Java 9 job. I also added a PR Jenkins job for Java 10 and will
soon disable the Java 9 PR job.
The general idea is to have a separate Jenkins job for the latest non LTS
release (Java 10) and all supported LTS releases (Java 8 and Java 7
currently, soon to become Java 8 only).
Let me know if you have any questions or concerns.