Bump http from 0.1.17 to 0.1.21 in /workshop_serveless/ex6

Bumps [http](https://github.com/hyperium/http) from 0.1.17 to 0.1.21.
- [Release notes](https://github.com/hyperium/http/releases)
- [Changelog](https://github.com/hyperium/http/blob/v0.1.21/CHANGELOG.md)
- [Commits](hyperium/http@v0.1.17...v0.1.21)

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

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Author: dependabot[bot]