information-schema-deadlocks: add the "Begin" step (#20412) (#20413)

Author: ti-chi-bot

information-schema/information-schema-deadlocks.md

@@ -124,6 +124,8 @@ INSERT INTO t VALUES (1, 10), (2, 20);
 
 | 事务 1                               | 事务 2                               | 说明                 |
 |--------------------------------------|--------------------------------------|----------------------|
+| `BEGIN;`                             |                                      |                      |
+|                                      | `BEGIN;`                             |                      |
 | `UPDATE t SET v = 11 WHERE id = 1;`  |                                      |                      |
 |                                      | `UPDATE t SET v = 21 WHERE id = 2;`  |                      |
 | `UPDATE t SET v = 12 WHERE id = 2;`  |                                      | 事务 1 阻塞          |