Update "Securing Euereka server" section in docs.

docs/src/main/asciidoc/spring-cloud-netflix.adoc

@@ -575,27 +575,26 @@ You can set your hostname at the run-time by using an environment variable -- fo
 === Securing The Eureka Server
 
 You can secure your Eureka server simply by adding Spring Security to your
-server's classpath via `spring-boot-starter-security`.  By default when Spring Security is on the classpath it will require that
+server's classpath via `spring-boot-starter-security`.  By default, when Spring Security is on the classpath it will require that
 a valid CSRF token be sent with every request to the app.  Eureka clients will not generally possess a valid
 cross site request forgery (CSRF) token you will need to disable this requirement for the `/eureka/**` endpoints.
 For example: 
 
 [source,java,indent=0]
 ----
-@EnableWebSecurity
-class WebSecurityConfig extends WebSecurityConfigurerAdapter {
-
-    @Override
-    protected void configure(HttpSecurity http) throws Exception {
-        http.csrf().ignoringAntMatchers("/eureka/**");
-        super.configure(http);
-    }
+@Bean
+public SecurityFilterChain securityFilterChain(HttpSecurity http) throws Exception {
+	http.authorizeHttpRequests((authz) -> authz
+        .anyRequest().authenticated())
+	    .httpBasic(withDefaults());
+    http.csrf().ignoringRequestMatchers("/eureka/**");
+    return http.build();
 }
 ----
 
 For more information on CSRF see the https://docs.spring.io/spring-security/site/docs/current/reference/htmlsingle/#csrf[Spring Security documentation].
 
-A demo Eureka Server can be found in the Spring Cloud Samples https://github.com/spring-cloud-samples/eureka/tree/Eureka-With-Security[repo].
+A demo Eureka Server can be found in the Spring Cloud Samples https://github.com/spring-cloud-samples/eureka/tree/Eureka-With-Security-4.x[repo].
 
 === JDK 11 Support