Remove the Groovydoc plugin use (#111)

* Update build.gradle

* Remove the Groovydoc plugin use

This plugin causes a resolution error failure when releasing.
We switch to Gradle's groovydoc task instead, which shouldn't
be a problem because we have almost no Groovy classes in the
public API and it seems that Groovy docs are not published
as part of the documentation we build in `docs`.

* Update Micronaut Gradle Plugin to 6.4.2

* Global exclude groovydoc gradle plugin

buildSrc/build.gradle

@@ -9,6 +9,7 @@ repositories {
 }
 
 configurations.all {
+    exclude group: "io.github.groovylang.groovydoc", module: "io.github.groovylang.groovydoc.gradle.plugin"
     resolutionStrategy {
         eachDependency { details ->
             if (details.requested.group == 'org.codehaus.groovy') {
@@ -31,7 +32,6 @@ dependencies {
     implementation "com.diffplug.spotless:spotless-plugin-gradle:6.17.0"
     implementation "io.spring.nohttp:nohttp-gradle:0.0.11"
     implementation "gradle.plugin.com.github.johnrengelman:shadow:7.1.2"
-    implementation "io.github.groovylang.groovydoc:io.github.groovylang.groovydoc.gradle.plugin:1.0.1"
     implementation "io.github.gradle-nexus:publish-plugin:1.3.0"
 }
 

buildSrc/src/main/groovy/org.grails.forge.internal.base-module.gradle

@@ -131,6 +131,6 @@ tasks.withType(GroovyCompile).configureEach {
     groovyOptions.forkOptions.jvmArgs.add('-Dgroovy.parameters=true')
 }
 
-tasks.withType(org.groovy.lang.groovydoc.tasks.GroovydocTask).configureEach {
+tasks.withType(Groovydoc).configureEach {
     classpath += project.configurations.documentation
 }