Bump pytest-xdist from 1.29.0 to 2.5.0

Bumps [pytest-xdist](https://github.com/pytest-dev/pytest-xdist) from 1.29.0 to 2.5.0.
- [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@v1.29.0...v2.5.0)

---
updated-dependencies:
- dependency-name: pytest-xdist
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

tests/requirements-test.txt

@@ -3,6 +3,6 @@ versioneer<0.18
 pytest==4.6.3
 pytest-catchlog==1.2.2
 pytest-timeout==1.3.4
-pytest-xdist==1.29.0
+pytest-xdist==2.5.0
 pytest-cov==3.0.0
 tox==3.26.0