fix(database): 修复封存表医疗记录ID非空约束导致插入错误

- 移除 mr_sealing 表中 medical_record_id 字段的 NOT NULL 约束
- 解决前端不传递该字段时的插入报错问题
- 允许封存业务通过病案号手动录入时 medicalRecordId 为空值

healthlink-his-server/healthlink-his-application/src/main/resources/db/migration/V42__bug745_fix_mr_sealing_medical_record_id.sql

@@ -1,3 +0,0 @@
--- Bug #745: mr_sealing.medical_record_id NOT NULL 导致前端不传该字段时 INSERT 报错
--- 封存业务通过病案号手动录入，medicalRecordId 非必需，改为可空
-ALTER TABLE mr_sealing ALTER COLUMN medical_record_id DROP NOT NULL;