Bump pytest-xdist from 2.3.0 to 2.4.0 in /requirements/CI-tests-pip

Bumps [pytest-xdist](https://github.com/pytest-dev/pytest-xdist) from 2.3.0 to 2.4.0.
- [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@v2.3.0...v2.4.0)

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

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

Author: dependabot[bot]

requirements/CI-tests-pip/requirements.txt

@@ -6,7 +6,7 @@ matplotlib==3.4.3
 numpy==1.21.2
 pandas==1.2.5
 pytest==6.2.5
-pytest-xdist==2.3.0
+pytest-xdist==2.4.0
 seaborn==0.11.2
 sortedcontainers==2.4.0
 tqdm==4.62.3