Update eslint-plugin-node to the latest version 🚀 (#22)

Author: greenkeeper[bot]

packages/google-cloud-node/package.json

@@ -77,7 +77,7 @@
     "codecov": "^3.0.0",
     "eslint": "^4.10.0",
     "eslint-config-prettier": "^2.7.0",
-    "eslint-plugin-node": "^5.2.1",
+    "eslint-plugin-node": "^6.0.0",
     "eslint-plugin-prettier": "^2.3.1",
     "ink-docstrap": "^1.3.0",
     "intelli-espower-loader": "^1.0.1",