Bump mongoose from 6.0.9 to 6.13.9 in /react-express-mongodb/backend

Bumps [mongoose](https://github.com/Automattic/mongoose) from 6.0.9 to 6.13.9.
- [Release notes](https://github.com/Automattic/mongoose/releases)
- [Changelog](https://github.com/Automattic/mongoose/blob/6.13.9/CHANGELOG.md)
- [Commits](https://github.com/Automattic/mongoose/compare/6.0.9...6.13.9)

---
updated-dependencies:
- dependency-name: mongoose
  dependency-version: 6.13.9
  dependency-type: direct:production
...

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

react-express-mongodb/backend/package.json

@@ -19,7 +19,7 @@
     "express": "^4.17.1",
     "lodash": "^4.17.13",
     "mongodb": "^3.0.7",
-    "mongoose": "^6.0.9",
+    "mongoose": "^6.13.9",
     "simple-node-logger": "^18.12.23",
     "validator": "^13.7.0"
   },