Apply hlint hints

All hints are applied in one single commit, as a commit per hint would
result in 80+ separate commits—tihs is really just too much noise.

Related: https://github.com/xmonad/xmonad-contrib/issues/537

XMonad/Layout/Stoppable.hs

@@ -120,7 +120,7 @@ instance LayoutModifier Stoppable Window where
           where run = sigStoppableWorkspacesHook m >> return Nothing
     handleMess (Stoppable m d _) msg
         | Just Hide <- fromMessage msg =
-            (Just . Stoppable m d . Just) <$> startTimer d
+            Just . Stoppable m d . Just <$> startTimer d
         | otherwise = return Nothing
 
 -- | Convert a layout to a stoppable layout using the default mark