Update Gradle Asciidoctor Plugin to 4.0.0-alpha.1
diff --git a/build.gradle b/build.gradle
index 8474da6..0bad79c 100644
--- a/build.gradle
+++ b/build.gradle
@@ -9,7 +9,7 @@
         classpath "io.github.groovylang.groovydoc:groovydoc-gradle-plugin:1.0.1"
         classpath "org.grails:grails-gradle-plugin:$grailsGradlePluginVersion"
         classpath "org.grails.plugins:views-gradle:2.3.2"
-        classpath 'org.asciidoctor:asciidoctor-gradle-plugin:1.6.1'
+        classpath("org.asciidoctor:asciidoctor-gradle-jvm:4.0.0-alpha.1")
         classpath "com.github.erdi:webdriver-binaries-gradle-plugin:3.0"
         classpath "org.gradle:test-retry-gradle-plugin:1.5.2"
     }
diff --git a/docs/build.gradle b/docs/build.gradle
index b60fbf6..e69ecab 100644
--- a/docs/build.gradle
+++ b/docs/build.gradle
@@ -14,8 +14,8 @@
 
 version rootProject.version
 
-apply plugin: 'org.asciidoctor.convert'
 apply plugin: 'groovy'
+apply plugin: 'org.asciidoctor.jvm.convert'
 
 configurations.all {
     resolutionStrategy.eachDependency { DependencyResolveDetails details ->
@@ -66,10 +66,6 @@
                 'sourcedir'     : "${project.projectDir}/src/main/groovy"
 }
 
-asciidoctorj {
-    version = '1.5.4'
-}
-
 task fetchSource {
     outputs.dir layout.buildDirectory.dir('checkout')
     inputs.properties(branch: githubBranch)