Getting pq: syntax error at or near "transaction" when running migration with transaction:false

**Description**

Having

```sql
--migrate:up transaction:false
```

in a dbmate migration file produces a syntax error.

- Version: dbmate version 2.4.0
- Database: postgres v13
- Operating System: macOS 12.6.3

**Steps To Reproduce**

1. Do a postgres migration with `CREATE INDEX CONCURRENTLY ...` in a dbmate migrations file:

```sql
-- migrate:up transaction:false

drop index concurrently my_index;

create index concurrently my_index on my_table (
some_column
);
```

2. Run with `dbmate --no-schema-dump up`.

**Actual Behavior**

```
Applying: 20230621121155_my_migration.sql
Error: pq: syntax error at or near "transaction"
```

It seems this is some bug/limitation with the `pq` lib, but I just wanted to give a heads up.