chore: bump pytest from 9.0.3 to 9.1.0 (#703)

Bumps [pytest](https://github.com/pytest-dev/pytest) from 9.0.3 to 9.1.0.
- [Release notes](https://github.com/pytest-dev/pytest/releases)
- [Changelog](https://github.com/pytest-dev/pytest/blob/main/CHANGELOG.rst)
- [Commits](pytest-dev/pytest@9.0.3...9.1.0)

---
updated-dependencies:
- dependency-name: pytest
  dependency-version: 9.1.0
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

pyproject.toml

@@ -81,7 +81,7 @@ full = [
 dev = [
     "xarray<2026.5",  # TODO: drop once linopy ships xarray 2026.3+ compat fix
     "tsam==3.4.0",  # Time series aggregation for clustering
-    "pytest==9.0.3",
+    "pytest==9.1.0",
     "pytest-xdist==3.8.0",
     "nbformat==5.10.4",
     "ruff==0.15.17",