Revert "Remove @Configuration from webflux config examples"

This reverts commit aec9effb88f70151912971b2f8b05dc4a9afaa2f.

docs/modules/ROOT/pages/reactive/configuration/webflux.adoc

@@ -64,6 +64,7 @@ The following page shows an explicit version of the minimal WebFlux Security con
 .Java
 [source,java,role="primary"]
 -----
+@Configuration
 @EnableWebFluxSecurity
 public class HelloWebfluxSecurityConfig {
 
@@ -93,6 +94,7 @@ public class HelloWebfluxSecurityConfig {
 .Kotlin
 [source,kotlin,role="secondary"]
 -----
+@Configuration
 @EnableWebFluxSecurity
 class HelloWebfluxSecurityConfig {
 
@@ -136,6 +138,7 @@ For example, you can isolate configuration for URLs that start with `/api`:
 .Java
 [source,java,role="primary"]
 ----
+@Configuration
 @EnableWebFluxSecurity
 static class MultiSecurityHttpConfig {
 
@@ -173,6 +176,7 @@ static class MultiSecurityHttpConfig {
 .Kotlin
 [source,kotlin,role="secondary"]
 ----
+@Configuration
 @EnableWebFluxSecurity
 open class MultiSecurityHttpConfig {
     @Order(Ordered.HIGHEST_PRECEDENCE)                                                      <1>