Bump pytest-xdist from 3.3.1 to 3.4.0

Bumps [pytest-xdist](https://github.com/pytest-dev/pytest-xdist) from 3.3.1 to 3.4.0.
- [Changelog](https://github.com/pytest-dev/pytest-xdist/blob/master/CHANGELOG.rst)
- [Commits](pytest-dev/pytest-xdist@v3.3.1...v3.4.0)

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

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