Bump chai from 4.4.1 to 5.1.1 in /backend

Bumps [chai](https://github.com/chaijs/chai) from 4.4.1 to 5.1.1.
- [Release notes](https://github.com/chaijs/chai/releases)
- [Changelog](https://github.com/chaijs/chai/blob/main/History.md)
- [Commits](chaijs/chai@v4.4.1...v5.1.1)

---
updated-dependencies:
- dependency-name: chai
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

backend/package.json

@@ -21,7 +21,7 @@
     "adm-zip": "^0.5.12",
     "bcrypt": "^5.1.1",
     "body-parser": "^1.20.2",
-    "chai": "^4.4.1",
+    "chai": "^5.1.1",
     "connect-mongo": "^5.1.0",
     "cors": "^2.8.5",
     "cucumber-html-reporter": "^7.1.1",