fix(deps): update dependency @google-cloud/promisify to ^0.4.0 (#218)

Author: renovate[bot]

packages/google-cloud-dns/package.json

@@ -48,7 +48,7 @@
   "dependencies": {
     "@google-cloud/common": "^0.31.0",
     "@google-cloud/paginator": "^0.1.0",
-    "@google-cloud/promisify": "^0.3.0",
+    "@google-cloud/promisify": "^0.4.0",
     "arrify": "^1.0.1",
     "dns-zonefile": "0.2.2",
     "lodash.groupby": "^4.6.0",