Update shadowJar to new config format

build.gradle

@@ -78,7 +78,7 @@ buildscript {
     }
 
     dependencies {
-        classpath 'com.github.jengelman.gradle.plugins:shadow:6.1.0'
+        classpath 'com.github.johnrengelman:shadow:8.1.1'
         classpath 'com.github.ben-manes:gradle-versions-plugin:0.51.0'
     }
 }
@@ -172,9 +172,9 @@ jar {
 }
 
 shadowJar {
-    baseName = project.name
-    classifier = null
-    version = null
+    archiveBaseName.set(project.name)
+    archiveClassifier.set('') // Set to an empty string if you don't need a classifier.
+    archiveVersion.set('') // Set to an empty string if you don't want the version in the jar name.
 }
 
 task debBuild(dependsOn: shadowJar) {