Bump xarray from 2024.5.0 to 2024.6.0 in /.github/dependabot

Bumps [xarray](https://github.com/pydata/xarray) from 2024.5.0 to 2024.6.0.
- [Release notes](https://github.com/pydata/xarray/releases)
- [Changelog](https://github.com/pydata/xarray/blob/main/HOW_TO_RELEASE.md)
- [Commits](pydata/xarray@v2024.05.0...v2024.06.0)

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

Signed-off-by: dependabot[bot] <[email protected]>

.github/dependabot/constraints.txt

@@ -21,4 +21,4 @@ pytz==2024.1
 pyzmq==26.0.3
 six==1.16.0
 tzdata==2024.1
-xarray==2024.5.0
+xarray==2024.6.0