HHH-2298 WARN if using build-in conn pool

Author: brmeyer

hibernate-core/src/main/java/org/hibernate/internal/CoreMessageLogger.java

@@ -1411,7 +1411,7 @@ void usingDefaultIdGeneratorSegmentValue(String tableName,
 	void usingDriver(String driverClassName,
 					 String url);
 
-	@LogMessage(level = INFO)
+	@LogMessage(level = WARN)
 	@Message(value = "Using Hibernate built-in connection pool (not for production use!)", id = 402)
 	void usingHibernateBuiltInConnectionPool();