Polish doc

See gh-4743

spring-boot-actuator/README.adoc

@@ -46,6 +46,6 @@ For Gradle, use the declaration:
   to an `AuditService`. Once Spring Security is in play it automatically publishes
   authentication events by default. This can be very useful for reporting, and also to
   implement a lock-out policy based on authentication failures.
-* **Process Monitoring** In Spring Boot Actuator you can find `ApplicationPidListener`
+* **Process Monitoring** In Spring Boot Actuator you can find `ApplicationPidFileWriter`
   which creates a file containing the application PID (by default in the application
   directory with a file name of `application.pid`).