Remove useless version override for MongoDBContainer

Closes gh-23520

Author: snicoll

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

@@ -43,7 +43,7 @@
 class DataMongoTestIntegrationTests {
 
 	@Container
-	static final MongoDBContainer mongoDB = new MongoDBContainer("mongo:4.0.10").withStartupAttempts(5)
+	static final MongoDBContainer mongoDB = new MongoDBContainer().withStartupAttempts(5)
 			.withStartupTimeout(Duration.ofMinutes(5));
 
 	@Autowired

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

@@ -40,7 +40,7 @@
 class DataMongoTestReactiveIntegrationTests {
 
 	@Container
-	static final MongoDBContainer mongoDB = new MongoDBContainer("mongo:4.0.10").withStartupAttempts(5)
+	static final MongoDBContainer mongoDB = new MongoDBContainer().withStartupAttempts(5)
 			.withStartupTimeout(Duration.ofMinutes(5));
 
 	@Autowired

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

@@ -41,7 +41,7 @@
 class DataMongoTestWithIncludeFilterIntegrationTests {
 
 	@Container
-	static final MongoDBContainer mongoDB = new MongoDBContainer("mongo:4.0.10").withStartupAttempts(5)
+	static final MongoDBContainer mongoDB = new MongoDBContainer().withStartupAttempts(5)
 			.withStartupTimeout(Duration.ofMinutes(5));
 
 	@Autowired

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

@@ -47,7 +47,7 @@
 class TransactionalDataMongoTestIntegrationTests {
 
 	@Container
-	static final MongoDBContainer mongoDB = new MongoDBContainer("mongo:4.0.10").withStartupAttempts(5)
+	static final MongoDBContainer mongoDB = new MongoDBContainer().withStartupAttempts(5)
 			.withStartupTimeout(Duration.ofMinutes(5));
 
 	@Autowired