requirements: update pytest-xdist requirement

Updates the requirements on [pytest-xdist](https://github.com/pytest-dev/pytest-xdist) to permit the latest version.
- [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@v3.2.0...v3.6.1)

---
updated-dependencies:
- dependency-name: pytest-xdist
  dependency-type: direct:development
...

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

dev_requirements.txt

@@ -8,4 +8,4 @@ pytest-helpers-namespace<2021.12.30
 pytest-profiling<1.7.1
 pytest-pycodestyle<2.4.0
 pytest-pydocstyle<2.4.0
-pytest-xdist>=3.2.0, <3.6.0
+pytest-xdist>=3.2.0, <3.7.0