Fix Javadoc links to Java API
Fix Javadoc links to Java API

Revert
https://github.com/gradle/gradle/commit/568a0b932fc7e879c7f212db14d19a9499ce1a3c
and use `--source 8` instead until fix makes his way to JDK used on CI.

gradle/gradle,robinverduijn/gradle,robinverduijn/gradle,robinverduijn/gradle,blindpirate/gradle,gradle/gradle,robinverduijn/gradle,robinverduijn/gradle,blindpirate/gradle,blindpirate/gradle,gradle/gradle,blindpirate/gradle,robinverduijn/gradle,gradle/gradle,blindpirate/gradle,gradle/gradle,robinverduijn/gradle,blindpirate/gradle,robinverduijn/gradle,gradle/gradle,robinverduijn/gradle,robinverduijn/gradle,gradle/gradle,gradle/gradle,blindpirate/gradle,gradle/gradle,blindpirate/gradle,robinverduijn/gradle,blindpirate/gradle,blindpirate/gradle,gradle/gradle