Bump express from 4.16.2 to 4.20.0 in /fixtures/expiration

Bumps [express](https://github.com/expressjs/express) from 4.16.2 to 4.20.0.
- [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/4.16.2...4.20.0

)

---
updated-dependencies:
- dependency-name: express
  dependency-type: indirect
...

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