wrong code logic but correct behavior

## Bug Report

Please answer these questions before submitting your issue. Thanks!

### 1. Minimal reproduce step (Required)

add comments like this


and enable `tidb_restricted_read_only` by

```
set global tidb_restricted_read_only = 1;
```

shall see


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

not calling into `allowInReadOnlyMode`

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

called into

### 4. What is your TiDB version? (Required)

master