Unpin, to see what happens

[aulemahal]

Pull Request Checklist:

• This PR addresses an already opened issue (for bug fixes / features)
  • This PR fixes #xyz
• (If applicable) Documentation has been added / updated (for bug fixes / features).
• (If applicable) Tests have been added.
• This PR does not seem to break the templates.
• CHANGELOG.rst has been updated (with summary of main changes).
  • Link to issue (:issue:number) and pull request (:pull:number) has been added.

What kind of change does this PR introduce?

• Unpin xarray, dask and zarr to see what happens.
• Change "<" pin of xESMF to "=!" as the bug is resolved in xESMF's master.

Does this PR introduce a breaking change?

Other information: