[Java] Upgrade to Shadow 6.1.0.

Author: mjpt777

build.gradle

@@ -22,7 +22,7 @@ buildscript {
 plugins {
  id 'java-library'
  id 'idea'
- id 'com.github.johnrengelman.shadow' version '6.0.0' apply false
+ id 'com.github.johnrengelman.shadow' version '6.1.0' apply false
  id "com.github.ben-manes.versions" version "0.33.0"
 }