chore(deps): bump express from 4.17.1 to 4.17.3 in /backend

Bumps [express](https://github.com/expressjs/express) from 4.17.1 to 4.17.3.
- [Release notes](https://github.com/expressjs/express/releases)
- [Changelog](https://github.com/expressjs/express/blob/master/History.md)
- [Commits](https://github.com/expressjs/express/compare/4.17.1...4.17.3)

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

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

backend/package.json

@@ -34,7 +34,7 @@
     "emoji-regex": "^8.0.0",
     "erlpack": "github:discord/erlpack",
     "escape-string-regexp": "^1.0.5",
-    "express": "^4.17.0",
+    "express": "^4.17.3",
     "fp-ts": "^2.0.1",
     "humanize-duration": "^3.15.0",
     "io-ts": "^2.0.0",