chore(package): update @types/helmet to version 0.0.39

Author: greenkeeper[bot]

package.json

@@ -21,7 +21,7 @@
     "@types/cors": "^2.8.3",
     "@types/dotenv": "^4.0.0",
     "@types/graphql": "^0.13.1",
-    "@types/helmet": "^0.0.38",
+    "@types/helmet": "^0.0.39",
     "@types/jest": "^23.1.3",
     "@types/supertest": "^2.0.2",
     "awesome-typescript-loader": "^5.2.0",