build: Remove redundant --harmony flag for node invocation

This is only for the test of node-qunit itself. Generators were
enabled by default as of Node 4.0.

<https://nodejs.org/en/blog/release/v4.0.0/>

Author: Krinkle

package.json

@@ -34,7 +34,7 @@
     "node": ">=0.6.0 < 8.0"
   },
   "scripts": {
-    "test": "node --harmony ./test/testrunner.js && eslint .",
+    "test": "node ./test/testrunner.js && eslint .",
     "lint": "eslint ."
   },
   "dependencies": {