chore(deps): bump express from 4.19.2 to 4.21.1 in /frontend

Bumps [express](https://github.com/expressjs/express) from 4.19.2 to 4.21.1.
- [Release notes](https://github.com/expressjs/express/releases)
- [Changelog](https://github.com/expressjs/express/blob/4.21.1/History.md)
- [Commits](expressjs/express@4.19.2...4.21.1)

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

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

frontend/examples/express/package.json

@@ -8,7 +8,7 @@
     "cookie-parser": "^1.4.6",
     "cors": "^2.8.5",
     "dotenv": "^16.0.2",
-    "express": "^4.19.2",
+    "express": "^4.21.1",
     "express-jwt": "^8.3.0",
     "jwks-rsa": "^3.1.0"
   }