Expected literal number, found: $1

test code:

```rust
#[test]
fn test_sql() {
let sql = "select distinct incident0_.incident_id as incident1_39_ from incident incident0_ where 1=1 order by incident0_.create_time desc limit $1";
Parser::parse_sql(&dialect, sql).unwrap();
}
```

result:

```text
called `Result::unwrap()` on an `Err` value: ParserError("Expected literal number, found: $1")
thread 'interceptor::pg::tests::test_sql' panicked at 'called `Result::unwrap()` on an `Err` value: ParserError("Expected literal number, found: $1")',
```

Start with the provided test case and the Parser::parse_sql entry point, then trace how the LIMIT expression handles the $1 parameter. The issue is done when this SQL parses successfully without the “Expected literal number” error.

Do mô hình lập chỉ mục viết ra từ nội dung của issue.