Update dependency express to v4.16.4

Author: renovate-bot

amp-paywall-demo/package.json

@@ -18,7 +18,7 @@
   "dependencies": {
     "body-parser": "1.18.3",
     "cookie-parser": "1.4.3",
-    "express": "4.16.3",
+    "express": "4.16.4",
     "gcloud": "^0.37.0",
     "hogan-express": "0.5.2",
     "hogan.js": "^3.0.2",

amp-pwa/package.json

@@ -6,7 +6,7 @@
   "license": "Apache-2.0",
   "proxy": "http://localhost:4000",
   "devDependencies": {
-    "express": "4.16.3",
+    "express": "4.16.4",
     "react-scripts": "2.1.3",
     "sw-precache": "5.2.1"
   },