Exclude starters from Javadoc aggregation

See gh-24648

spring-boot-project/spring-boot-docs/build.gradle

@@ -117,6 +117,7 @@ task aggregatedJavadoc(type: Javadoc) {
 		Set<Project> publishedProjects = rootProject.subprojects.findAll { it != project}
 			.findAll { it.plugins.hasPlugin(JavaPlugin) && it.plugins.hasPlugin(MavenPublishPlugin) }
 			.findAll { !excludedProjects.contains(it.name) }
+			.findAll { !it.name.startsWith('spring-boot-starter') }
 		dependsOn publishedProjects.javadoc
 		source publishedProjects.javadoc.source
 		classpath = project.files(publishedProjects.javadoc.classpath)