Fix visibility of a type exposed as a bean

Closes gh-27189

Author: snicoll

spring-boot-project/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/health/HealthEndpointConfiguration.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2020 the original author or authors.
+ * Copyright 2012-2021 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -102,7 +102,7 @@ static HealthEndpointGroupsBeanPostProcessor healthEndpointGroupsBeanPostProcess
 	 * {@link BeanPostProcessor} to invoke {@link HealthEndpointGroupsPostProcessor}
 	 * beans.
 	 */
-	private static class HealthEndpointGroupsBeanPostProcessor implements BeanPostProcessor {
+	static class HealthEndpointGroupsBeanPostProcessor implements BeanPostProcessor {
 
 		private final ObjectProvider<HealthEndpointGroupsPostProcessor> postProcessors;