Simplify root project after move to Antora

See gh-1009

Author: wilkinsona

build.gradle

@@ -1,9 +1,3 @@
-plugins {
-	id 'base'
-	id 'maven-publish'
-	id 'org.springframework.restdocs.conventions'
-}
-
 allprojects {
 	group = "org.springframework.restdocs"
 	repositories {
@@ -13,29 +7,3 @@ allprojects {
 		}
 	}
 }
-
-task api (type: Javadoc) {
-	group = "Documentation"
-	description = "Generates aggregated Javadoc API documentation."
-	project.rootProject.gradle.projectsEvaluated {
-		Set<String> excludedProjects = ['spring-restdocs-asciidoctor']
-		Set<Project> publishedProjects = rootProject.subprojects.findAll { it != project}
-			.findAll { it.plugins.hasPlugin(JavaPlugin) && it.plugins.hasPlugin(MavenPublishPlugin) }
-			.findAll { !excludedProjects.contains(it.name) }
-		dependsOn publishedProjects.javadoc
-		source publishedProjects.javadoc.source
-		classpath = project.files(publishedProjects.javadoc.classpath)
-		destinationDir = project.file "${buildDir}/docs/javadoc"
-		options {
-			author = true
-			docTitle = "Spring REST Docs ${project.version} API"
-			encoding = "UTF-8"
-			memberLevel = "protected"
-			outputLevel = "quiet"
-			source = "17"
-			splitIndex = true
-			use = true
-			windowTitle = "Spring REST Docs ${project.version} API"
-		}
-	}
-}