Remove `@EnableWebFlux` from documentation code snippets

Like what we did for `@EnableWebMvc`, we want to remove `@EnableWebFlux`
from typical code snippets extending WebFluxConfigurer to make them more
Spring Boot friendly.

Closes gh-36091

framework-docs/modules/ROOT/pages/web/webflux-cors.adoc

@@ -305,7 +305,6 @@ Java::
 [source,java,indent=0,subs="verbatim,quotes"]
 ----
 	@Configuration
-	@EnableWebFlux
 	public class WebConfig implements WebFluxConfigurer {
 
 		@Override
@@ -328,7 +327,6 @@ Kotlin::
 [source,kotlin,indent=0,subs="verbatim,quotes"]
 ----
 	@Configuration
-	@EnableWebFlux
 	class WebConfig : WebFluxConfigurer {
 
 		override fun addCorsMappings(registry: CorsRegistry) {

framework-docs/modules/ROOT/pages/web/webflux-functional.adoc

@@ -639,7 +639,6 @@ Java::
 [source,java,indent=0,subs="verbatim,quotes"]
 ----
 	@Configuration
-	@EnableWebFlux
 	public class WebConfig implements WebFluxConfigurer {
 
 		@Bean
@@ -676,7 +675,6 @@ Kotlin::
 [source,kotlin,indent=0,subs="verbatim,quotes"]
 ----
 	@Configuration
-	@EnableWebFlux
 	class WebConfig : WebFluxConfigurer {
 
 		@Bean

framework-docs/modules/ROOT/pages/web/webflux/reactive-spring.adoc

@@ -658,7 +658,6 @@ Java::
 [source,java,indent=0,subs="verbatim,quotes"]
 ----
 	@Configuration
-	@EnableWebFlux
 	class MyConfig implements WebFluxConfigurer {
 
 		@Override
@@ -673,7 +672,6 @@ Kotlin::
 [source,kotlin,indent=0,subs="verbatim,quotes"]
 ----
 	@Configuration
-	@EnableWebFlux
 	class MyConfig : WebFluxConfigurer {
 
 		override fun configureHttpMessageCodecs(configurer: ServerCodecConfigurer) {