Bump yaml in /code-samples/eventing/bookstore-sample-app/start/frontend

Bumps [yaml](https://github.com/eemeli/yaml) from 2.4.1 to 2.8.3.
- [Release notes](https://github.com/eemeli/yaml/releases)
- [Commits](eemeli/yaml@v2.4.1...v2.8.3)

---
updated-dependencies:
- dependency-name: yaml
  dependency-version: 2.8.3
  dependency-type: indirect
...

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Author: dependabot[bot]