fix:fix Feign.Builder.class not found error

spring-cloud-tencent-starters/spring-cloud-tencent-feign/src/main/java/com/tencent/cloud/feign/PluggableFeignAutoConfiguration.java

@@ -29,18 +29,14 @@ import org.springframework.context.annotation.Configuration;
  * @author Haotian Zhang
  */
 @Configuration
+@ConditionalOnProperty(name = "com.tencent.cloud.feign.enabled", matchIfMissing = true)
+@ConditionalOnClass(Feign.class)
 public class PluggableFeignAutoConfiguration {
 
-    @Configuration
-    @ConditionalOnProperty(name = "com.tencent.cloud.feign.enabled", matchIfMissing = true)
-    static class PluggableFeignConfig {
-
     @Bean
     @ConditionalOnMissingBean
     public Feign.Builder pluggableFeignBuilder() {
         return PluggableFeign.builder();
     }
 
-    }
-
 }