Polish MetricsAutoConfiguration

Align `meterRegistryPostProcessor` with `meterRegistryCloser`, the
`@Bean` method shouldn't be public if the return type is not public.

See gh-45521

Signed-off-by: Yanming Zhou <[email protected]>

Author: quaff

spring-boot-project/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/metrics/MetricsAutoConfiguration.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2022 the original author or authors.
+ * Copyright 2012-2025 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.
@@ -56,7 +56,7 @@ public Clock micrometerClock() {
 	}
 
 	@Bean
-	public static MeterRegistryPostProcessor meterRegistryPostProcessor(ApplicationContext applicationContext,
+	static MeterRegistryPostProcessor meterRegistryPostProcessor(ApplicationContext applicationContext,
 			ObjectProvider<MetricsProperties> metricsProperties,
 			ObjectProvider<MeterRegistryCustomizer<?>> meterRegistryCustomizers,
 			ObjectProvider<MeterFilter> meterFilters, ObjectProvider<MeterBinder> meterBinders) {