RFR 8189262: jdk.jlink module-info.java javadoc comment refers to the non-existent jmage tool doc

[Sundararajan Athijegannathan]

Please review:

Webrev: http://cr.openjdk.java.net/~sundar/8189262/webrev.00/
Bug: https://bugs.openjdk.java.net/browse/JDK-8189262

Thanks,
-Sundar