Bump express and reveal-md in /presentations

Bumps [express](https://github.com/expressjs/express) to 4.19.2 and updates ancestor dependency [reveal-md](https://github.com/webpro/reveal-md). These dependencies need to be updated together.


Updates `express` from 4.18.2 to 4.19.2
- [Release notes](https://github.com/expressjs/express/releases)
- [Changelog](https://github.com/expressjs/express/blob/master/History.md)
- [Commits](expressjs/express@4.18.2...4.19.2)

Updates `reveal-md` from 6.1.0 to 6.1.1
- [Release notes](https://github.com/webpro/reveal-md/releases)
- [Changelog](https://github.com/webpro/reveal-md/blob/main/.release-it.json)
- [Commits](webpro/reveal-md@6.1.0...6.1.1)

---
updated-dependencies:
- dependency-name: express
  dependency-type: indirect
- dependency-name: reveal-md
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>