Fix visibility of imported things

Related to this idris change : https://github.com/idris-lang/Idris-dev/commit/7b5f4aa392985c6a7d7fdd5268cebe4adee954b8

Without that change test will fail with:

```
No such variable Control.Monad.Identity.Identity instance of Prelude.Monad.Monad
```

or `Control.Monad.Identity` should be imported in test too