Align test for spring.data.mongodb.autoIndexCreation with new default

Closes gh-28481

Author: wilkinsona

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/data/mongo/MongoDataAutoConfigurationTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2020 the original author or authors.
+ * Copyright 2012-2021 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.
@@ -147,13 +147,21 @@ void customFieldNamingStrategy() {
 	}
 
 	@Test
-	void customAutoIndexCreation() {
-		this.contextRunner.withPropertyValues("spring.data.mongodb.autoIndexCreation:false").run((context) -> {
+	void defaultAutoIndexCreation() {
+		this.contextRunner.run((context) -> {
 			MongoMappingContext mappingContext = context.getBean(MongoMappingContext.class);
 			assertThat(mappingContext.isAutoIndexCreation()).isFalse();
 		});
 	}
 
+	@Test
+	void customAutoIndexCreation() {
+		this.contextRunner.withPropertyValues("spring.data.mongodb.autoIndexCreation:true").run((context) -> {
+			MongoMappingContext mappingContext = context.getBean(MongoMappingContext.class);
+			assertThat(mappingContext.isAutoIndexCreation()).isTrue();
+		});
+	}
+
 	@Test
 	void interfaceFieldNamingStrategy() {
 		this.contextRunner