Fix Javadoc generation with Java 17

This project removes all customizations that were tailored for Java 8
Javadoc generation.

Fixes gh-494

Author: bclozel

build.gradle

@@ -70,7 +70,7 @@ configure(moduleProjects) {
 	ext.javadocLinks = [
 			"https://docs.oracle.com/en/java/javase/17/docs/api/",
 			"https://docs.spring.io/spring-framework/docs/6.0.x/javadoc-api/",
-			"https://javadoc.io/doc/com.graphql-java/graphql-java/18.1/"
+			"https://javadoc.io/doc/com.graphql-java/graphql-java/19.2/"
 	] as String[]
 
 	components.java.withVariantsFromConfiguration(configurations.testFixturesApiElements) { skip() }

spring-graphql-docs/build.gradle

@@ -57,14 +57,9 @@ task api(type: Javadoc) {
 		author = true
 		header = rootProject.description
 		use = true
-		overview = "src/docs/api/overview.html"
-		stylesheetFile = file("src/docs/api/stylesheet.css")
 		splitIndex = true
 		links(project.ext.javadocLinks)
 		addStringOption('Xdoclint:none', '-quiet')
-		if(JavaVersion.current().isJava9Compatible()) {
-			addBooleanOption('html5', true)
-		}
 	}
 	source = moduleProjects.collect { project ->
 		project.sourceSets.main.allJava