build(deps): bump express in /superset-websocket/utils/client-ws-app

Bumps [express](https://github.com/expressjs/express) from 4.20.0 to 4.21.0.
- [Release notes](https://github.com/expressjs/express/releases)
- [Changelog](https://github.com/expressjs/express/blob/4.21.0/History.md)
- [Commits](expressjs/express@4.20.0...4.21.0)

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

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

superset-websocket/utils/client-ws-app/package.json

@@ -8,7 +8,7 @@
   "dependencies": {
     "cookie-parser": "~1.4.6",
     "debug": "~4.3.6",
-    "express": "~4.20.0",
+    "express": "~4.21.0",
     "http-errors": "~2.0.0",
     "jsonwebtoken": "^9.0.2",
     "morgan": "~1.10.0",