Bump qs and express in /example/oauth-backend

Bumps [qs](https://github.com/ljharb/qs) to 6.16.0 and updates ancestor dependency [express](https://github.com/expressjs/express). These dependencies need to be updated together.


Updates `qs` from 6.15.2 to 6.16.0
- [Changelog](https://github.com/ljharb/qs/blob/main/CHANGELOG.md)
- [Commits](ljharb/qs@v6.15.2...v6.16.0)

Updates `express` from 4.22.2 to 5.2.1
- [Release notes](https://github.com/expressjs/express/releases)
- [Changelog](https://github.com/expressjs/express/blob/master/History.md)
- [Commits](expressjs/express@v4.22.2...v5.2.1)

---
updated-dependencies:
- dependency-name: qs
  dependency-version: 6.16.0
  dependency-type: indirect
- dependency-name: express
  dependency-version: 5.2.1
  dependency-type: direct:production
...

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

Author: dependabot[bot]