Update pytest-xdist requirement from <2.3,>=2.2.1 to >=2.2.1,<2.4 (#1378)

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](https://github.com/pytest-dev/pytest-xdist/compare/v2.2.1...v2.3.0)

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

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

setup.py

@@ -70,7 +70,7 @@ setup(
         "docs": ["sphinx_rtd_theme", "sphinx-autobuild"],
         "test": [
             "pytest>=5.2.2,<6.3.0",
-            "pytest-xdist>=2.2.1,<2.3",
+            "pytest-xdist>=2.2.1,<2.4",
             "pytest-asyncio>=0.10,<0.16",
             "beautifulsoup4>=4.8.1,<4.10.0",
             "black==21.6b0",