Fix ScheduledTasksEndpointTests BaseConfiguration

Update the `BaseConfiguration` class in `ScheduledTasksEndpointTests`
to be package private so that it can be enhanced by cglib.

Prior to merge commit 361437f4 the class was a lite configuration so
it didn't matter that it was a private class.

spring-boot-project/spring-boot-actuator/src/test/java/org/springframework/boot/actuate/scheduling/ScheduledTasksEndpointTests.java

@@ -144,7 +144,7 @@ public class ScheduledTasksEndpointTests {
 
 	@Configuration
 	@EnableScheduling
-	private static class BaseConfiguration {
+	static class BaseConfiguration {
 
 		@Bean
 		public ScheduledTasksEndpoint endpoint(