Don't let comments escape from empty export lists

[amesgen]

Closes #906, see #933 (comment) for more context. The main advantage of this PR to #933 is that it is much more minimal, bu it is still relatively ad-hoc.

There is a similar issue in other cases, e.g. also with this PR (or also with #933), comments "escape" here:

data Foo = Foo {
  -- foo
  }

foo = [
  -- foo
  ]

foo = (
  -- foo
  )

See 54dfe3e for an approach to call encloseLocated "automatically" via an overlapping instance, which e.g. "catches" the comment in the first case in the example above. The other two would probably need ad-hoc handling in p_rdrName.

[github-actions]

🚀 Deployed on https://5f70b3d792ae8646db3d71a9aeb80f407b8a6fe9--ormolu-live.netlify.app