Privilege check is mistakenly skipped for the plan cache point get special path

## Bug Report

Please answer these questions before submitting your issue. Thanks!

### 1. Minimal reproduce step (Required)

conn1
`mysql -h 127.0.0.1 -P 4000 -u root`
```sql
use test;
CREATE USER 'testuser'@'%';
CREATE TABLE test.t1 (a INT, b INT, PRIMARY KEY(a));
GRANT SELECT ON test.t1 TO 'testuser'@'%';
```

conn2
`mysql -h 127.0.0.1 -P 4000 -u testuser`
```sql
use test;
PREPARE stmt1 FROM 'SELECT * FROM test.t1 WHERE a = 0';
EXECUTE stmt1;
```

conn1
```
REVOKE SELECT ON test.t1 FROM 'testuser'@'%';
```

conn2
```
EXECUTE stmt1;
```

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

`ERROR 1142 (42000): SELECT command denied to user 'testuser'@'127.0.0.1' for table 't1'`

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

Successfully executed.

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

From v4.0 until the latest nightly (pre v9.0)