chore(package): update snyk to version 1.21.2

https://greenkeeper.io/

Author: greenkeeperio-bot

package.json

@@ -35,6 +35,6 @@
   "devDependencies": {
     "ava": "^0.13.0",
     "nyc": "^6.0.0",
-    "snyk": "^1.13.1"
+    "snyk": "^1.21.2"
   }
 }