Connect closed due to error of "Async commit/1PC result undetermined"

## Bug Report

Please answer these questions before submitting your issue. Thanks!

### 1. Minimal reproduce step (Required)

### 2. What did you expect to see? (Required)
Should not report undetermined error even conflict occur.

### 3. What did you see instead (Required)

```
2025-11-02 16:05:27 (UTC+08:00)TiDB 10.107.17.6:4000[2pc.go:1544] ["Async commit/1PC result undetermined"] [conn=2338774952] [session_alias=] [error="write conflict { start_ts:461916268819120199 conflict_ts:461916268819120196 key:\"t...\" conflict_commit_ts:461916268819120200 reason:Optimistic }"] [rpcErr="cached region not found"] [txnStartTS=461916268819120199]

2025-11-02 16:05:27 (UTC+08:00)TiDB 10.107.17.6:4000[conn.go:1108] ["result undetermined, close this connection"] [conn=2338774952] [session_alias=] [error="[global:2]execution result undetermined"]
```
### 4. What is your TiDB version? (Required)
v7.5.6