[Java] Upgrade to javadoc-links 3.6.6.

Author: mjpt777

build.gradle

@@ -22,7 +22,7 @@ buildscript {
 plugins {
  id 'java'
  id 'com.gradle.build-scan' version '2.3'
- id "io.freefair.javadoc-links" version "3.6.4" apply false
+ id "io.freefair.javadoc-links" version "3.6.6" apply false
  id 'com.github.johnrengelman.shadow' version '5.0.0' apply false
 }