fix: move nut-js to optional spec deps (#41199)

spec/package.json

@@ -11,7 +11,6 @@
     "@electron-ci/is-valid-window": "file:./is-valid-window",
     "@electron-ci/uv-dlopen": "file:./fixtures/native-addon/uv-dlopen/",
     "@marshallofsound/mocha-appveyor-reporter": "^0.4.3",
-    "@nut-tree/nut-js": "^3.1.2",
     "@types/sinon": "^9.0.4",
     "@types/ws": "^7.2.0",
     "basic-auth": "^2.0.1",
@@ -39,6 +38,9 @@
     "ws": "^7.4.6",
     "yargs": "^16.0.3"
   },
+  "optionalDependencies": {
+    "@nut-tree/nut-js": "^3.1.2"
+  },
   "resolutions": {
     "nan": "file:../../third_party/nan",
     "dbus-native/optimist/minimist": "1.2.7",