Update dependency bull to v3.16.0

Author: renovate-bot

package-lock.json

@@ -51,7 +51,7 @@
     "axios": "0.19.0",
     "bignumber.js": "9.0.0",
     "bluebird": "3.5.5",
-    "bull": "3.12.1",
+    "bull": "3.16.0",
     "cheerio": "1.0.0-rc.3",
     "config": "3.1.0",
     "dotenv-safe": "6.1.0",