io-sim-por: fixed execAtomically'

As of ac6ec44 `execAtomically'` should not run `commitTVar`.

Author: coot

io-sim/src/Control/Monad/IOSimPOR/Internal.hs

@@ -1531,7 +1531,6 @@ execAtomically' = go Map.empty
        -> ST s [SomeTVar s]
     go !written action = case action of
       ReturnStm () -> do
-        !_ <- traverse_ (\(SomeTVar tvar) -> commitTVar tvar) written
         return (Map.elems written)
       ReadTVar v k  -> do
         x <- execReadTVar v