Refine example to show @NestedConfigurationProperty usage

Closes gh-33239

spring-boot-project/spring-boot-docs/src/docs/asciidoc/native-image/advanced-topics.adoc

@@ -6,7 +6,7 @@
 [[native-image.advanced.nested-configuration-properties]]
 === Nested Configuration Properties
 Reflection hints are automatically created for configuration properties by the Spring ahead-of-time engine.
-Nested configuration properties, however, *must* be annotated with `@NestedConfigurationProperty`, otherwise they won't be detected and will not be bindable.
+Nested configuration properties which are no inner classes, however, *must* be annotated with `@NestedConfigurationProperty`, otherwise they won't be detected and will not be bindable.
 
 include::code:MyProperties[]
 

spring-boot-project/spring-boot-docs/src/main/java/org/springframework/boot/docs/nativeimage/advanced/nestedconfigurationproperties/MyProperties.java

@@ -41,7 +41,9 @@ public class MyProperties {
 	}
 	// @fold:off
 
-	public static class Nested {
+}
+
+class Nested {
 
 	private int number;
 
@@ -55,6 +57,4 @@ public class MyProperties {
 	}
 	// @fold:off
 
-	}
-
 }