String argument to limit is not resulting error.

## Bug Report

Please answer these questions before submitting your issue. Thanks!
```sql
prepare s from "select 1 limit ?";
set @a='qwe';
execute s using @a;
```

### 2. What did you expect to see? (Required)
```sql
mysql> execute s using @a;
ERROR 1210 (HY000): Incorrect arguments to EXECUTE
```
### 3. What did you see instead (Required)
```sql
mysql> execute s using @a;
Empty set, 2 warnings (0.00 sec)

mysql> show warnings;
+---------+------+-----------------------------------------+
| Level | Code | Message |
+---------+------+-----------------------------------------+
| Warning | 1292 | Truncated incorrect DOUBLE value: 'qwe' |
| Warning | 1292 | Truncated incorrect DOUBLE value: 'qwe' |
+---------+------+-----------------------------------------+
2 rows in set (0.00 sec)
```
### 4. What is your TiDB version? (Required)

```sql
| Release Version: v6.1.0-alpha-482-g81a852077-dirty
Edition: Community
Git Commit Hash: 81a852077ac0632a16242f28c660449d9ee14398
Git Branch: master
UTC Build Time: 2022-05-25 21:38:33
GoVersion: go1.18.1
Race Enabled: false
TiKV Min Version: v3.0.0-60965b006877ca7234adaced7890d7b029ed1306
Check Table Before Drop: false |
```