chore(package): update mongoose to version 5.2.11

Author: greenkeeper[bot]

dref/api/package.json

@@ -20,7 +20,7 @@
  "express": "~4.16.0",
  "express-validator": "^5.2.0",
  "http-errors": "~1.7.0",
- "mongoose": "^5.1.2",
+ "mongoose": "^5.2.11",
  "morgan": "~1.9.0",
  "nodemon": "^1.17.4",
  "pug": "^2.0.3",