Bump body-parser and express in /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 1.20.2 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@1.20.2...1.20.3)

Updates `express` from 4.19.2 to 4.21.0
- [Release notes](https://github.com/expressjs/express/releases)
- [Changelog](https://github.com/expressjs/express/blob/4.21.0/History.md)
- [Commits](expressjs/express@4.19.2...4.21.0)

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

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