Bump mongodb from 6.9.0 to 6.11.0 in /backend

Bumps [mongodb](https://github.com/mongodb/node-mongodb-native) from 6.9.0 to 6.11.0.
- [Release notes](https://github.com/mongodb/node-mongodb-native/releases)
- [Changelog](https://github.com/mongodb/node-mongodb-native/blob/main/HISTORY.md)
- [Commits](mongodb/node-mongodb-native@v6.9.0...v6.11.0)

---
updated-dependencies:
- dependency-name: mongodb
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

backend/package.json

@@ -52,7 +52,7 @@
     "jsrsasign": "^11.1.0",
     "lodash-es": "^4.17.21",
     "mjml": "^4.15.3",
-    "mongodb": "^6.9.0",
+    "mongodb": "^6.11.0",
     "mongoose": "^6.13.5",
     "mongoose-delete": "^1.0.2",
     "morgan": "^1.10.0",