Fix lovelaceToAda function
The old version of this function had type `Micro -> Ada`, but that type allowed its use in `lovelaceToAda . MkFixed . fromIntegral` AND as `lovelaceToAda . fromIntegral` with the former giving INCORRECT results. By switching the type to `Integer -> Ada` it is no longer possible to use this function incorrectly. Related: https://github.com/IntersectMBO/cardano-db-sync/issues/2031