net/spread-j: only compiles on jdk8 and jdk11

Error on later JDKs:
[javac] /wrkdirs/usr/ports/net/spread-j/work/spread-src-3.17.3/java/spread/SpreadConnection.java:1800: error: invalid use of a restricted identifier 'yield'
[javac] yield();

PR: 272855
Approved-by: no maintainer