refactor(workflow): 移除未使用的日期时间变量

- 删除了未被引用的 currentDate 和 yearMonth 变量
- 简化了业务编号生成逻辑
- 清理了冗余的时间格式化代码

OpenAuth.App/workflow/WorkflowEngineApp.cs

@@ -74,8 +74,6 @@ public class WorkflowEngineApp : SqlSugarBaseApp<SysCategoryType, SugarDbContext
                 .First();
             if (startNode == null)
                 throw new Exception("流程开始节点【区县提交】不存在，请配置节点");
-            var currentDate = DateTime.Now;
-            var yearMonth = currentDate.ToString("yyyyMM");
             var prefix = "wfjszl";
             var businessNo = _businessNoGenerator.GenerateBusinessNo(prefix);
             requestDto.BusinessNo = businessNo;