Failure to parse lines without indentation in `do` block.

It's common to write SQL queries with Esqueleto without indent lines under a `do`, like this:

```haskell
getJohns =
select $ do
people <- from $ table @Person
where_ (people ^. PersonName ==. val "John")
pure people
```

This style more closely resembles what you might write in plain SQL.

Running stylish-haskell on this fails however, with something like the following error message:

```
:22:9: error:
parse error on input `<-'
Perhaps this statement should be within a 'do' block?
```