企业微信-移除可省略的错误判断 (#734)

Co-authored-by: markwang <www.wang61@qq.com>

work/externalcontact/follow_user.go

@@ -31,8 +31,5 @@ func (r *Client) GetFollowUserList() ([]string, error) {
 	}
 	var result followerUserResponse
 	err = util.DecodeWithError(response, &result, "GetFollowUserList")
-	if err != nil {
-		return nil, err
-	}
-	return result.FollowUser, nil
+	return result.FollowUser, err
 }