补全用户与岗位的关联的单元测试，简化相关的实现代码

yudao-module-system/yudao-module-system-biz/src/test/resources/sql/create_tables.sql

@@ -225,7 +225,7 @@ CREATE TABLE IF NOT EXISTS `system_operate_log` (
     PRIMARY KEY (`id`)
 ) COMMENT ='操作日志记录';
 
-CREATE TABLE IF NOT EXISTS "system_user" (
+CREATE TABLE IF NOT EXISTS "system_users" (
     "id" bigint not null GENERATED BY DEFAULT AS IDENTITY,
     "username" varchar(30) not null,
     "password" varchar(100) not null default '',