SOME operator with collation is resulting error.

## Bug Report

Please answer these questions before submitting your issue. Thanks!

### 1. Minimal reproduce step (Required)
```sql
drop table if exists t1;
CREATE TABLE t1 (a CHAR(1) CHARSET latin1, b CHAR(1) CHARSET utf8);
SELECT a FROM t1 WHERE a < SOME(SELECT '1');
```

### 2. What did you expect to see? (Required)
```sql
mysql> SELECT a FROM t1 WHERE a < SOME(SELECT '1');
Empty set (0.00 sec)
```

### 3. What did you see instead (Required)
```sql
mysql> SELECT a FROM t1 WHERE a < SOME(SELECT '1');
ERROR 1267 (HY000): Illegal mix of collations (latin1_bin,IMPLICIT) and (utf8mb4_general_ci,COERCIBLE) for operation '<'
```
### 4. What is your TiDB version? (Required)

```sql
| Release Version: v5.5.0-alpha-182-gad9430039
Edition: Community
Git Commit Hash: ad9430039f54bb9af78d44831c176bc5eafcbba0
Git Branch: master
UTC Build Time: 2022-02-18 17:57:13
GoVersion: go1.17.2
Race Enabled: false
TiKV Min Version: v3.0.0-60965b006877ca7234adaced7890d7b029ed1306
Check Table Before Drop: false |
```