chore(deps): update pytest-xdist requirement from ==3.7.* to ==3.8.* (#165)

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@v3.7.0...v3.8.0)

---
updated-dependencies:
- dependency-name: pytest-xdist
  dependency-version: 3.8.0
  dependency-type: direct:production
...

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Charles Moore <122481442+moorec-aws@users.noreply.github.com>

Author: dependabot[bot]

requirements-testing.txt

@@ -2,7 +2,7 @@ coverage[toml] == 7.*
 pytest == 8.4.*
 pytest-cov == 6.2.*
 pytest-timeout == 2.4.*
-pytest-xdist == 3.7.*
+pytest-xdist == 3.8.*
 types-PyYAML == 6.*
 black == 25.*
 ruff == 0.12.*