update comment

Author: kaisecheng

.ci/common/logstash.Dockerfile

@@ -4,7 +4,7 @@ USER logstash
 COPY --chown=logstash:logstash Gemfile /usr/share/plugins/plugin/Gemfile
 COPY --chown=logstash:logstash *.gemspec VERSION* version* /usr/share/plugins/plugin/
 RUN cp /usr/share/logstash/logstash-core/versions-gem-copy.yml /usr/share/logstash/versions.yml
-# NOTE: since 8.0 JDK is bundled as part of the LS distribution under $LS_HOME/jdk
+# NOTE: since 7.10 JDK is bundled as part of the LS distribution under $LS_HOME/jdk
 ENV PATH="${PATH}:/usr/share/logstash/vendor/jruby/bin:/usr/share/logstash/jdk/bin"
 ENV LOGSTASH_SOURCE="1"
 RUN gem install bundler -v '< 2'