Simplify note comment on macos sytem assertion

Also make use of when instead.

Co-authored-by: Sebastian Nagel <[email protected]>

hydra-cluster/src/HydraNode.hs

@@ -305,11 +305,9 @@ withHydraNode' ::
   (Handle -> Maybe Handle -> ProcessHandle -> IO a) ->
   IO a
 withHydraNode' chainConfig workDir hydraNodeId hydraSKey hydraVKeys allNodeIds pparams mGivenStdOut action = do
-  case os of
-    -- XXX: this is to not bind to port 5000 on darwin systems,
-    -- as it might already be in use on recent macOS devices.
-    "darwin" -> hydraNodeId `shouldNotBe` 0
-    _ -> pure ()
+  -- NOTE: AirPlay on MacOS uses 5000 and we must avoid it.
+  when (os == "darwin") $
+    port `shouldNotBe` 5000
   withSystemTempDirectory "hydra-node" $ \dir -> do
     let cardanoLedgerProtocolParametersFile = dir </> "pparams.json"
     writeFileBS cardanoLedgerProtocolParametersFile (writeZeroedPParams pparams)