Polish spring-boot-docs

See gh-25089

spring-boot-project/spring-boot-docs/src/docs/asciidoc/howto.adoc

@@ -95,7 +95,7 @@ For instance, the following example loads a YAML configuration file from the cla
 
 [source,java,indent=0]
 ----
-include::{include-howto}/springbootapplication/ExampleEnvironmentPostProcessor.java[tag=*]
+include::{include-howto}/springbootapplication/MyEnvironmentPostProcessor.java[tag=*]
 ----
 
 TIP: The `Environment` has already been prepared with all the usual property sources that Spring Boot loads by default.

spring-boot-project/spring-boot-docs/src/docs/asciidoc/production-ready-features.adoc

@@ -463,7 +463,7 @@ The following example exposes a read operation that returns a custom object:
 
 [source,java,indent=0]
 ----
-include::{include-productionreadyfeatures}/endpoints/CustomEndpointExample.java[tag=read]
+include::{include-productionreadyfeatures}/endpoints/CustomEndpoint.java[tag=read]
 ----
 
 You can also write technology-specific endpoints by using `@JmxEndpoint` or `@WebEndpoint`.
@@ -500,7 +500,7 @@ This can be used to invoke a write operation that takes `String name` and `int c
 
 [source,java,indent=0]
 ----
-include::{include-productionreadyfeatures}/endpoints/CustomEndpointExample.java[tag=write]
+include::{include-productionreadyfeatures}/endpoints/CustomEndpoint.java[tag=write]
 ----
 
 TIP: Because endpoints are technology agnostic, only simple types can be specified in the method signature.

spring-boot-project/spring-boot-docs/src/docs/asciidoc/spring-boot-features.adoc

@@ -436,7 +436,7 @@ This exit code can then be passed to `System.exit()` to return it as a status co
 
 [source,java,indent=0]
 ----
-include::{include-springbootfeatures}/springapplication/ExitCodeExample.java[tag=*]
+include::{include-springbootfeatures}/springapplication/exitcode/MyApplication.java[tag=*]
 ----
 
 Also, the `ExitCodeGenerator` interface may be implemented by exceptions.