Fix showing of arguments with type parameters

[chshersh]

Currently when data type has argument with specialized type parameter, it doesn't show correctly:

λ: newtype Id a = Id { unId :: String } deriving (Generic) deriving anyclass (Elm)
λ: data User = User { userId :: Id User } deriving (Generic) deriving anyclass (Elm)
λ: T.putStrLn $ prettyShowDefinition $ toElmDefinition (Proxy @User)
type alias User =
    { id : Id
    }

Expected output:

type alias User =
    { id : Id User
    }

Looks like the problem is in Generic instance for record field. I will try to fix it.