Fix sidecar example in 2021.x (#3266)

spring-cloud-alibaba-examples/spring-cloud-alibaba-sidecar-examples/spring-cloud-alibaba-sidecar-nacos-example/pom.xml

@@ -34,6 +34,10 @@
             <groupId>com.alibaba.cloud</groupId>
             <artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId>
         </dependency>
+        <dependency>
+            <groupId>org.springframework.cloud</groupId>
+            <artifactId>spring-cloud-starter-loadbalancer</artifactId>
+        </dependency>
 
         <dependency>
             <groupId>org.springframework.boot</groupId>

spring-cloud-alibaba-examples/spring-cloud-alibaba-sidecar-examples/spring-cloud-alibaba-sidecar-nacos-example/src/main/resources/application.yml

@@ -12,6 +12,11 @@ spring:
       discovery:
         locator:
           enabled: true
+    loadbalancer:
+      nacos:
+        enabled: true
+      ribbon:
+        enabled: false
 
   application:
     name: node-service