Bump pytest-xdist from 2.1.0 to 2.2.0 (#220)

Bumps [pytest-xdist](https://github.com/pytest-dev/pytest-xdist) from 2.1.0 to 2.2.0.
- [Release notes](https://github.com/pytest-dev/pytest-xdist/releases)
- [Changelog](https://github.com/pytest-dev/pytest-xdist/blob/master/CHANGELOG.rst)
- [Commits](pytest-dev/pytest-xdist@v2.1.0...v2.2.0)

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

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]