Bump luxon from 2.5.2 to 3.5.0 in /packages/backend

Bumps [luxon](https://github.com/moment/luxon) from 2.5.2 to 3.5.0.
- [Changelog](https://github.com/moment/luxon/blob/master/CHANGELOG.md)
- [Commits](moment/luxon@2.5.2...3.5.0)

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

Signed-off-by: dependabot[bot] <[email protected]>

packages/backend/package.json

@@ -30,7 +30,7 @@
     "dockerode": "^3.3.1",
     "express": "^4.17.1",
     "express-promise-router": "^4.1.0",
-    "luxon": "^2.0.2",
+    "luxon": "^3.5.0",
     "winston": "^3.2.1"
   },
   "devDependencies": {