Upgrade to Gradle 6.8 and modernize the build

Closes gh-719

docs/src/test/java/com/example/webtestclient/ExampleApplicationTestNgTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2014-2019 the original author or authors.
+ * Copyright 2014-2021 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -41,8 +41,7 @@ public class ExampleApplicationTestNgTests {
 
 	@BeforeMethod
 	public void setUp(Method method) {
-		this.webTestClient = WebTestClient.bindToApplicationContext(this.context)
-				.configureClient()
+		this.webTestClient = WebTestClient.bindToApplicationContext(this.context).configureClient()
 				.filter(documentationConfiguration(this.restDocumentation)) // <1>
 				.build();
 		this.restDocumentation.beforeTest(getClass(), method.getName());