Fix reordering of statements inside FROM statement

The following spec fails

```ruby
visit 'select', '1 FROM "b", (SELECT 1) "a", "c"', pg_node: 'PgQuery::RANGE_VAR'
```

with the following error from RSpec

```
      expected: "SELECT 1 FROM \"b\", (SELECT 1) \"a\", \"c\""
           got: "SELECT 1 FROM \"b\", \"c\" (SELECT 1) \"a\""
```

For some reason the subquery inside of the `FROM` moves to the back. 