Bump mongoose from 5.7.5 to 5.13.20

Bumps [mongoose](https://github.com/Automattic/mongoose) from 5.7.5 to 5.13.20.
- [Release notes](https://github.com/Automattic/mongoose/releases)
- [Changelog](https://github.com/Automattic/mongoose/blob/master/CHANGELOG.md)
- [Commits](Automattic/mongoose@5.7.5...5.13.20)

---
updated-dependencies:
- dependency-name: mongoose
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

package.json

@@ -13,7 +13,7 @@
     "express-session": "^1.12.1",
     "jade": "~1.11.0",
     "mongodb": "^3.1.13",
-    "mongoose": "^5.7.5",
+    "mongoose": "^5.13.20",
     "mongoskin": "^1.3.20",
     "monk": "https://github.com/vccabral/monk.git",
     "morgan": "~1.6.1",