Update pytest requirement from <8,>=6 to >=6,<9

Updates the requirements on [pytest](https://github.com/pytest-dev/pytest) to permit the latest version.
- [Release notes](https://github.com/pytest-dev/pytest/releases)
- [Changelog](https://github.com/pytest-dev/pytest/blob/main/CHANGELOG.rst)
- [Commits](pytest-dev/pytest@6.0.0...8.0.0)

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

Signed-off-by: dependabot[bot] <support@github.com>

setup.py

@@ -89,7 +89,7 @@
             "twine<5",
         ],
         "test": [
-            "pytest>=6,<8",
+            "pytest>=6,<9",
             "pytest-cov>=2,<5",
             "re-assert>=1,<2",
         ],