adjust deployment type

this is a cop-out possible until
fricklerhandwerk/Fediversity#15.
after that, this will require actually figuring out how to get `options`
for `deployment.nix` - which may need `evalModules` with
`data-model.nix`.

deployment/check/data-model/deployment.nix

@@ -146,6 +146,7 @@ let
           };
         };
         "example-deployment" = mkOption {
+          type = config.environments.single-nixos-vm.resource-mapping.output-type;
           default = config.environments.single-nixos-vm.deployment config."example-configuration";
         };
       };