Update pytest requirement from <8 to <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@1.0.0b3...8.0.0)

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

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

pyproject.toml

@@ -122,7 +122,7 @@ scientific = [
   "xarray<2025",
 ]
 test = [
-  "pytest<8",
+  "pytest<9",
   "pytest-cov<5",
   "pytest-timeout<3",
 ]