build(deps-dev): bump pytest-docker in /services/staging

Bumps [pytest-docker](https://github.com/avast/pytest-docker) from 3.1.2 to 3.2.0.
- [Release notes](https://github.com/avast/pytest-docker/releases)
- [Changelog](https://github.com/avast/pytest-docker/blob/master/CHANGELOG.md)
- [Commits](avast/pytest-docker@v3.1.2...v3.2.0)

---
updated-dependencies:
- dependency-name: pytest-docker
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]