Bump mongoose from 5.7.11 to 5.13.15

Bumps [mongoose](https://github.com/Automattic/mongoose) from 5.7.11 to 5.13.15.
- [Release notes](https://github.com/Automattic/mongoose/releases)
- [Changelog](https://github.com/Automattic/mongoose/blob/master/CHANGELOG.md)
- [Commits](Automattic/mongoose@5.7.11...5.13.15)

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

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

package.json

@@ -19,7 +19,7 @@
     "express-session": "^1.17.0",
     "moment": "^2.24.0",
     "mongodb": "^3.3.4",
-    "mongoose": "^5.7.11",
+    "mongoose": "^5.13.15",
     "multer": "^1.4.2"
   }
 }