[Docs] Update links to java9 docs (elastic#28750)

Closes elastic#28683

Author: Lokesh Mohanty

docs/Versions.asciidoc

@@ -23,7 +23,7 @@ release-state can be: released | prerelease | unreleased
 Javadoc roots used to generate links from Painless's API reference
 ///////
 :java8-javadoc: https://docs.oracle.com/javase/8/docs/api
-:java9-javadoc: http://download.java.net/java/jigsaw/docs/api
+:java9-javadoc: https://docs.oracle.com/javase/9/docs/api
 :joda-time-javadoc: http://www.joda.org/joda-time/apidocs
 :lucene-core-javadoc: http://lucene.apache.org/core/{lucene_version_path}/core