chore(deps): bump express in /tests/apps/dockerfile-dokku-scale

Bumps [express](https://github.com/expressjs/express) from 4.17.3 to 4.18.1.
- [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/4.17.3...4.18.1)

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

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

tests/apps/dockerfile-dokku-scale/package.json

@@ -2,7 +2,7 @@
   "name": "node-example",
   "version": "0.0.1",
   "dependencies": {
-    "express": "4.17.x"
+    "express": "4.18.x"
   },
   "engines": {
     "node": "4.2.x"