Update validator background initializer

Update the validator background initializer to actually create
the validator.

Closes gh-11412

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/BackgroundPreinitializer.java

@@ -135,7 +135,7 @@ public class BackgroundPreinitializer
 
 		@Override
 		public void run() {
-			Validation.byDefaultProvider().configure();
+			Validation.byDefaultProvider().configure().buildValidatorFactory();
 		}
 
 	}