Bump org.asciidoctor:asciidoctor-gradle-jvm-epub from 3.3.2 to 4.0.4

Bumps org.asciidoctor:asciidoctor-gradle-jvm-epub from 3.3.2 to 4.0.4.

---
updated-dependencies:
- dependency-name: org.asciidoctor:asciidoctor-gradle-jvm-epub
  dependency-version: 4.0.4
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

build.gradle

@@ -7,7 +7,7 @@ buildscript {
         classpath "org.grails:grails-gradle-plugin:$grailsGradlePluginVersion"
         classpath 'org.asciidoctor:asciidoctor-gradle-jvm:3.3.2'
         classpath 'org.asciidoctor:asciidoctor-gradle-jvm-pdf:3.3.2'
-        classpath 'org.asciidoctor:asciidoctor-gradle-jvm-epub:3.3.2'
+        classpath 'org.asciidoctor:asciidoctor-gradle-jvm-epub:4.0.4'
         classpath 'org.ajoberstar:gradle-git:1.7.2'
         classpath "org.grails.plugins:hibernate5:${gormHibernateVersion-".RELEASE"}"
         classpath "de.undercouch:gradle-download-task:5.1.0"