Update dependency cookie-parser to v1.4.6

Author: renovate[bot]

amp-paywall-demo/package.json

@@ -17,7 +17,7 @@
   },
   "dependencies": {
     "body-parser": "1.18.3",
-    "cookie-parser": "1.4.3",
+    "cookie-parser": "1.4.6",
     "express": "4.16.4",
     "gcloud": "^0.37.0",
     "hogan-express": "0.5.2",