snowhawk: remove configuration hostPlatform

I handle this at the flake level

hosts/little-lightning/configuration.nix

@@ -28,8 +28,4 @@
   system.configurationRevision = self.rev or self.dirtyRev or null;
   # $ darwin-rebuild changelog
   system.stateVersion = 5;
-
-
-  # The platform the configuration will be used on.
-  # nixpkgs.hostPlatform = "x86_64-darwin";
 }