### Environment

* Dubbo version: dubbo-registry-nacos 2.7.6
* Operating System version: Win10
* Java version: JAVA 8

### Steps to reproduce this issue
1 springboot  yml配置如下： 
registry:
     address: nacos://127.0.0.1:8848
     simplified: true
     group: dubbo-local
  metadata-report:
            address: nacos://127.0.0.1:8848
            group: dubbo-local

2 登陆nacos 1.2.1 控制台发现元数据 group配置生效，但是服务管理下的group依旧是DEFAULT_GROUP。

3 跟了下dubbo-registry-nacos 2.7.6的代码 发现在调用NamingService中 没有传入配置的group参数，使用的默认组参数 
 public void doRegister(URL url) {
        String serviceName = this.getServiceName(url);
        Instance instance = this.createInstance(url);
        this.execute((namingService) -> {
            namingService.registerInstance(serviceName, instance);
        });
    }

Pls. provide [GitHub address] to reproduce this issue.

### Expected Result

What do you expected from the above steps？

### Actual Result

What actually happens?

If there is an exception, please attach the exception trace:

```
Just put your stack trace here!
```

filterHealthyInstances(healthyInstances);
        }
        List<URL> urls = toUrlWithEmpty(url, healthyInstances);
        NacosRegistry.this.notify(url, listener, urls);
    }
    /**
     * Get the categories from {@link URL}
     *
     * @param url {@link URL}
     * @return non-null array
     */
    private List<String> getCategories(URL url) {
        return ANY_VALUE.equals(url.getServiceInterface()) ?
                ALL_SUPPORTED_CATEGORIES : Arrays.asList(DEFAULT_CATEGORY);
    }
    private URL buildURL(Instance instance) {
        Map<String, String> metadata = instance.getMetadata();
        String protocol = metadata.get(PROTOCOL_KEY);
        String path = metadata.get(PATH_KEY);
        return new URL(protocol,
                instance.getIp(),
                instance.getPort(),
                path,
                instance.getMetadata());
    }
    private Instance createInstance(URL url) {
        
        String category = url.getParameter(CATEGORY_KEY, DEFAULT_CATEGORY);
        URL newURL = url.addParameter(CATEGORY_KEY, category);
        newURL = newURL.addParameter(PROTOCOL_KEY, url.getProtocol());