Mark the empty child registry row as not required

Why: task-pr-check --final requires 必需 to be 是 or 否.
Evidence: make task-pr-check FINAL=1 reported the invalid value.
Impact: Task card only.
Refs: scripts/task_pr_check.py
Co-authored-by: Cursor <cursoragent@cursor.com>

.task/feature-regulations-kb.md

@@ -35,7 +35,7 @@
 
 | 子任务分支 | 必需 | 状态 | PR |
 |---|---|---|---|
-| 无（各单元在组件仓独立分支交付，见「跨仓交付登记」） | — | — | — |
+| 无（各单元在组件仓独立分支交付，见「跨仓交付登记」） | 否 | — | — |
 
 ## Agent 实施收据