chore(deps): bump pin-project from 1.1.8 to 1.1.9 in /backend

Bumps [pin-project](https://github.com/taiki-e/pin-project) from 1.1.8 to 1.1.9.
- [Release notes](https://github.com/taiki-e/pin-project/releases)
- [Changelog](https://github.com/taiki-e/pin-project/blob/main/CHANGELOG.md)
- [Commits](taiki-e/pin-project@v1.1.8...v1.1.9)

---
updated-dependencies:
- dependency-name: pin-project
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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