chore(deps): bump body-parser and express in /frontend/mock-backend

Bumps [body-parser](https://github.com/expressjs/body-parser) to 1.20.3 and updates ancestor dependency [express](https://github.com/expressjs/express). These dependencies need to be updated together.


Updates `body-parser` from 1.18.2 to 1.20.3
- [Release notes](https://github.com/expressjs/body-parser/releases)
- [Changelog](https://github.com/expressjs/body-parser/blob/master/HISTORY.md)
- [Commits](expressjs/body-parser@1.18.2...1.20.3)

Updates `express` from 4.16.3 to 4.20.0
- [Release notes](https://github.com/expressjs/express/releases)
- [Changelog](https://github.com/expressjs/express/blob/master/History.md)
- [Commits](expressjs/express@4.16.3...4.20.0)

---
updated-dependencies:
- dependency-name: body-parser
  dependency-type: indirect
- dependency-name: express
  dependency-type: direct:production
...

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