unstable test TestHistoryReader

## Bug Report

Please answer these questions before submitting your issue. Thanks!

### 1. Minimal reproduce step (Required)

### 2. What did you expect to see? (Required)

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

```
=== RUN TestHistoryReader
reader_test.go:302:
Error Trace: util/stmtsummary/v2/reader_test.go:302
util/stmtsummary/v2/reader_test.go:306
Error: "[]" should have 2 item(s), but has 0
Test: TestHistoryReader
reader_test.go:271:
Error Trace: util/stmtsummary/v2/reader_test.go:271
GOROOT/src/runtime/panic.go:522
GOROOT/src/testing/testing.go:980
util/stmtsummary/v2/reader_test.go:302
util/stmtsummary/v2/reader_test.go:306
Error: Received unexpected error:
remove tidb-statements.log: no such file or directory
Test: TestHistoryReader
reader_test.go:260:
Error Trace: util/stmtsummary/v2/reader_test.go:260
GOROOT/src/runtime/panic.go:522
GOROOT/src/testing/testing.go:980
util/stmtsummary/v2/reader_test.go:271
GOROOT/src/runtime/panic.go:522
GOROOT/src/testing/testing.go:980
util/stmtsummary/v2/reader_test.go:302
util/stmtsummary/v2/reader_test.go:306
Error: Received unexpected error:
remove tidb-statements-2022-12-27T16-21-20.245.log: no such file or directory
Test: TestHistoryReader
```
### 4. What is your TiDB version? (Required)