Polish "Fix Spring Data Cassandra auto-configure condition"

See gh-16971

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/data/cassandra/CassandraDataAutoConfiguration.java

 /*
- * Copyright 2012-2017 the original author or authors.
+ * Copyright 2012-2019 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.

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/data/cassandra/CassandraDataAutoConfigurationTests.java

@@ -106,12 +106,10 @@ public class CassandraDataAutoConfigurationTests {
 	}
 
 	@Test
-	void clusterDoesNotExist() {
-		AnnotationConfigApplicationContext ctx = new AnnotationConfigApplicationContext();
-		ctx.register(CassandraDataAutoConfiguration.class);
-		ctx.refresh();
-		this.context = ctx;
-		assertThat(ctx.getBeansOfType(Session.class)).isEmpty();
+	public void clusterDoesNotExist() {
+		this.context = new AnnotationConfigApplicationContext(
+				CassandraDataAutoConfiguration.class);
+		assertThat(this.context.getBeansOfType(Session.class)).isEmpty();
 	}
 
 	public void load(Class<?>... config) {