chore(package): update nyc to version 12.0.2 (#84)

Author: greenkeeper[bot]

packages/google-cloud-node/package.json

@@ -85,7 +85,7 @@
     "intelli-espower-loader": "^1.0.1",
     "jsdoc": "^3.5.5",
     "mocha": "^5.0.0",
-    "nyc": "^11.3.0",
+    "nyc": "^12.0.2",
     "power-assert": "^1.4.4",
     "prettier": "^1.7.4",
     "safe-buffer": "^5.1.1",