module_header comment in export list incorrectly placed

If the exported element has a comment assigned to it (placed on the same line), after formatting the comment is placed one line below the exported element

## Example:

*Before:*
```
module Ouroboros.Consensus.ByronSpec.Ledger.Block (
ByronSpecBlock(..)
, ByronSpecHeader -- type alias
, Header(..)
, BlockConfig(..)
```
*After:*
```
module Ouroboros.Consensus.ByronSpec.Ledger.Block (
ByronSpecBlock (..)
, ByronSpecHeader
-- type alias
, BlockConfig (..)
) where
```