CI: (deps): Bump xarray from 2025.12.0 to 2026.1.0 in /ci

Bumps [xarray](https://github.com/pydata/xarray) from 2025.12.0 to 2026.1.0.
- [Release notes](https://github.com/pydata/xarray/releases)
- [Commits](pydata/xarray@v2025.12.0...v2026.01.0)

---
updated-dependencies:
- dependency-name: xarray
  dependency-version: 2026.1.0
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

ci/extra_requirements.txt

@@ -1,2 +1,2 @@
 netCDF4==1.7.4
-xarray==2025.12.0
+xarray==2026.1.0