Correct base Java version in JDK 18 CI image

ci/images/ci-image-jdk18/Dockerfile

@@ -3,7 +3,7 @@ FROM ubuntu:focal-20220113
 ADD setup.sh /setup.sh
 ADD get-jdk-url.sh /get-jdk-url.sh
 ADD get-docker-url.sh /get-docker-url.sh
-RUN ./setup.sh java8 java18
+RUN ./setup.sh java17 java18
 
 ENV JAVA_HOME /opt/openjdk
 ENV PATH $JAVA_HOME/bin:$PATH