MNT: (deps): Bump xarray from 0.17.0 to 0.20.1 in /ci
MNT: (deps): Bump xarray from 0.17.0 to 0.20.1 in /ci

Bumps [xarray](https://github.com/pydata/xarray) from 0.17.0 to 0.20.1.
- [Release notes](https://github.com/pydata/xarray/releases)
- [Changelog](https://github.com/pydata/xarray/blob/main/HOW_TO_RELEASE.md)
- [Commits](https://github.com/pydata/xarray/compare/v0.17.0...v0.20.1)

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

Signed-off-by: dependabot[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@github.com>
Unidata/siphon