remove unused eslint-plugin-standard

see standard/standard#1316

Author: voxpelli

package.json

@@ -22,7 +22,6 @@
     "eslint-plugin-node": "~11.1.0",
     "eslint-plugin-promise": "~4.2.1",
     "eslint-plugin-react": "~7.21.5",
-    "eslint-plugin-standard": "~4.0.2",
     "standard-engine": "^14.0.0"
   },
   "devDependencies": {