fix(deps): update dependency pumpify to v2 (#409)

Author: renovate-bot

packages/google-cloud-node/package.json

@@ -44,7 +44,7 @@
     "@google-cloud/common": "^2.0.0",
     "google-gax": "^1.0.0",
     "protobufjs": "^6.8.6",
-    "pumpify": "^1.5.1",
+    "pumpify": "^2.0.0",
     "stream-events": "^1.0.4"
   },
   "devDependencies": {