Use Mongo 3.5.5 by default with Embedded mongo

Closes gh-14476

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/mongo/embedded/EmbeddedMongoProperties.java

@@ -38,7 +38,7 @@ public class EmbeddedMongoProperties {
 	/**
 	 * Version of Mongo to use.
 	 */
-	private String version = "3.6.5";
+	private String version = "3.5.5";
 
 	private final Storage storage = new Storage();
 

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/mongo/embedded/EmbeddedMongoAutoConfigurationTests.java

@@ -60,12 +60,12 @@ public class EmbeddedMongoAutoConfigurationTests {
 
 	@Test
 	public void defaultVersion() {
-		assertVersionConfiguration(null, "3.6.5");
+		assertVersionConfiguration(null, "3.5.5");
 	}
 
 	@Test
 	public void customVersion() {
-		assertVersionConfiguration("3.6.3", "3.6.3");
+		assertVersionConfiguration("3.4.15", "3.4.15");
 	}
 
 	@Test